feat: switch code quality setup to ultracite and biome

.agents/skills/ultracite/SKILL.md

@@ -0,0 +1,106 @@
+---
+name: ultracite
+description: "Ultracite is a zero-config linting and formatting preset for JavaScript/TypeScript projects. Use when: (1) Setting up or initializing Ultracite in a project (ultracite init), (2) Running linting or formatting commands (check, fix, doctor), (3) Writing or reviewing JS/TS code in a project that uses Ultracite — to follow its code standards, (4) Troubleshooting linting/formatting issues, (5) User mentions 'ultracite', 'lint', 'format', 'code quality', or 'biome/eslint/oxlint' in a project with Ultracite installed."
+---
+
+# Ultracite
+
+Zero-config linting and formatting for JS/TS projects. Supports three linter backends: **Biome** (recommended), **ESLint** + Prettier, and **Oxlint** + Oxfmt.
+
+## Detecting Ultracite
+
+Check if `ultracite` is in `package.json` devDependencies. Detect the active linter by looking for:
+
+- `biome.jsonc` → Biome
+- `eslint.config.mjs` → ESLint
+- `.oxlintrc.json` → Oxlint
+
+## CLI Commands
+
+```bash
+# Check for issues (read-only)
+bunx ultracite check
+
+# Auto-fix issues
+bunx ultracite fix
+
+# Diagnose setup problems
+bunx ultracite doctor
+
+# Initialize in a new project
+bunx ultracite init
+```
+
+Replace `bunx` with `npx`, `pnpx`, or `yarn dlx` depending on the package manager.
+
+`check` and `fix` accept optional file paths: `bunx ultracite check src/index.ts`.
+
+## Initialization
+
+`bunx ultracite init` runs an interactive setup. For non-interactive (CI) use, pass flags:
+
+```bash
+bunx ultracite init \
+  --pm bun \
+  --linter biome \
+  --editors vscode cursor \
+  --agents claude copilot \
+  --frameworks react next \
+  --integrations husky lint-staged \
+  --quiet
+```
+
+**Flags:**
+
+- `--pm` — `npm` | `yarn` | `pnpm` | `bun`
+- `--linter` — `biome` (recommended) | `eslint` | `oxlint`
+- `--editors` — `vscode` | `zed` | `cursor` | `windsurf` | `antigravity` | `kiro` | `trae` | `void`
+- `--agents` — `claude` | `codex` | `copilot` | `cline` | `amp` | `gemini` | `cursor-cli` + 19 more
+- `--frameworks` — `react` | `next` | `solid` | `vue` | `svelte` | `qwik` | `remix` | `angular` | `astro` | `nestjs`
+- `--integrations` — `husky` | `lefthook` | `lint-staged` | `pre-commit`
+- `--hooks` — Enable auto-fix hooks for supported agents/editors
+- `--type-aware` — Enable type-aware linting (oxlint only)
+- `--skip-install` — Skip dependency installation
+- `--quiet` — Suppress prompts (auto-detected when `CI=true`)
+
+Init creates config that extends Ultracite presets:
+
+```jsonc
+// biome.jsonc
+{ "extends": ["ultracite/biome/core", "ultracite/biome/react"] }
+```
+
+Framework presets available per linter: `core`, `react`, `next`, `solid`, `vue`, `svelte`, `qwik`, `remix`, `angular`, `astro`, `nestjs`.
+
+## Code Standards
+
+When writing code in a project with Ultracite, follow these standards. For the full rules reference, see [references/code-standards.md](references/code-standards.md).
+
+Key rules at a glance:
+
+**Formatting:** 2-space indent, semicolons, double quotes, 80-char width, ES5 trailing commas, LF line endings.
+
+**Style:** Arrow functions preferred. `const` by default, never `var`. `for...of` over `.forEach()`. Template literals over concatenation. No enums (use objects with `as const`). No nested ternaries. Kebab-case filenames.
+
+**Correctness:** No unused imports/variables. No `any` (use `unknown`). Always `await` promises in async functions. No `console.log`/`debugger`/`alert` in production.
+
+**React:** Function components only. Hooks at top level. Exhaustive deps. `key` on iterables (no array index). No nested component definitions. Semantic HTML + ARIA.
+
+**Performance:** No accumulating spread in loops. No barrel files. No namespace imports. Top-level regex.
+
+**Security:** `rel="noopener"` on `target="_blank"`. No `dangerouslySetInnerHTML`. No `eval()`.
+
+## Troubleshooting
+
+Run `bunx ultracite doctor` to diagnose. It checks:
+
+1. Linter installation (biome/eslint/oxlint binary available)
+2. Config validity (extends ultracite presets correctly)
+3. Ultracite in package.json dependencies
+4. Conflicting tools (old `.eslintrc.*`, `.prettierrc.*` files)
+
+Common fixes:
+
+- **Conflicting configs**: Delete legacy `.eslintrc.*` and `.prettierrc.*` files after migrating to Ultracite
+- **Missing dependency**: Run `bunx ultracite init` again or manually add `ultracite` to devDependencies
+- **Rules not applying**: Ensure config file extends the correct presets for your framework

.agents/skills/ultracite/references/code-standards.md

@@ -0,0 +1,120 @@
+# Ultracite Code Standards
+
+## Core Principles
+
+Write code that is **accessible, performant, type-safe, and maintainable**. Focus on clarity and explicit intent over brevity.
+
+## Type Safety & Explicitness
+
+- Use explicit types for function parameters and return values when they enhance clarity
+- Prefer `unknown` over `any` when the type is genuinely unknown
+- Use const assertions (`as const`) for immutable values and literal types
+- Leverage TypeScript's type narrowing instead of type assertions
+- Use meaningful variable names instead of magic numbers — extract constants with descriptive names
+
+## Modern JavaScript/TypeScript
+
+- Use arrow functions for callbacks and short functions
+- Prefer `for...of` loops over `.forEach()` and indexed `for` loops
+- Use optional chaining (`?.`) and nullish coalescing (`??`) for safer property access
+- Prefer template literals over string concatenation
+- Use destructuring for object and array assignments
+- Use `const` by default, `let` only when reassignment is needed, never `var`
+
+## Async & Promises
+
+- Always `await` promises in async functions — don't forget to use the return value
+- Use `async/await` syntax instead of promise chains for better readability
+- Handle errors appropriately in async code with try-catch blocks
+- Don't use async functions as Promise executors
+
+## React & JSX
+
+- Use function components over class components
+- Call hooks at the top level only, never conditionally
+- Specify all dependencies in hook dependency arrays correctly
+- Use the `key` prop for elements in iterables (prefer unique IDs over array indices)
+- Nest children between opening and closing tags instead of passing as props
+- Don't define components inside other components
+- Use semantic HTML and ARIA attributes for accessibility:
+  - Provide meaningful alt text for images
+  - Use proper heading hierarchy
+  - Add labels for form inputs
+  - Include keyboard event handlers alongside mouse events
+  - Use semantic elements (`<button>`, `<nav>`, etc.) instead of divs with roles
+
+## Error Handling & Debugging
+
+- Remove `console.log`, `debugger`, and `alert` statements from production code
+- Throw `Error` objects with descriptive messages, not strings or other values
+- Use `try-catch` blocks meaningfully — don't catch errors just to rethrow them
+- Prefer early returns over nested conditionals for error cases
+
+## Code Organization
+
+- Keep functions focused and under reasonable cognitive complexity limits (max 20)
+- Extract complex conditions into well-named boolean variables
+- Use early returns to reduce nesting
+- Prefer simple conditionals over nested ternary operators
+- Group related code together and separate concerns
+
+## Security
+
+- Add `rel="noopener"` when using `target="_blank"` on links
+- Avoid `dangerouslySetInnerHTML` unless absolutely necessary
+- Don't use `eval()` or assign directly to `document.cookie`
+- Validate and sanitize user input
+
+## Performance
+
+- Avoid spread syntax in accumulators within loops
+- Use top-level regex literals instead of creating them in loops
+- Prefer specific imports over namespace imports
+- Avoid barrel files (index files that re-export everything)
+- Use proper image components (e.g., Next.js `<Image>`) over `<img>` tags
+
+## Formatting
+
+- 2-space indentation
+- LF line endings
+- 80-character line width
+- Semicolons always
+- Double quotes (single quotes in JSX)
+- ES5 trailing commas
+- Arrow parentheses always
+- Bracket spacing enabled
+
+## Style Rules
+
+- No enums — use objects with `as const`
+- No nested ternary operators
+- No non-null assertions (`!`)
+- Kebab-case filenames enforced
+- `useImportType` for type-only imports
+- Readonly class properties by default
+- Sorted imports, JSX attributes, interface members, and object properties
+
+## Framework-Specific
+
+**Next.js:** Use `<Image>` component for images. Use App Router metadata API for head elements. Use Server Components for async data fetching.
+
+**React 19+:** Use ref as a prop instead of `React.forwardRef`.
+
+**Solid/Svelte/Vue/Qwik:** Use `class` and `for` attributes (not `className` or `htmlFor`).
+
+## Testing
+
+- Write assertions inside `it()` or `test()` blocks
+- Avoid done callbacks in async tests — use async/await instead
+- Don't use `.only` or `.skip` in committed code
+- Keep test suites reasonably flat — avoid excessive `describe` nesting
+
+## Overrides
+
+Ultracite relaxes rules in specific contexts:
+
+- **Config files** (`*.config.{js,ts,...}`): Relaxed export and complexity rules
+- **Test files** (`*.test.*`, `__tests__/**`): No cognitive complexity limit, `console` and `any` allowed
+- **Scripts/bin files**: `console` and `process.env` allowed
+- **Storybook files**: Unused variable/import rules relaxed
+- **Build output** (`dist/`, `.next/`, `node_modules/`): Formatter and linter disabled entirely

.devcontainer/README.md

@@ -13,7 +13,7 @@ This devcontainer configuration provides a complete development environment for
 ### Development Tools
 
 - TypeScript support with the latest TypeScript extension
-- ESLint and Prettier for code formatting and linting
+- Ultracite (Biome backend) for code formatting and linting
 - Docker extension for container management
 - GitHub Actions extension for workflow support
 - JSON and YAML editing support

.devcontainer/devcontainer.json

@@ -18,23 +18,61 @@
     "vscode": {
       "extensions": [
         "ms-vscode.vscode-typescript",
-        "esbenp.prettier-vscode",
-        "dbaeumer.vscode-eslint",
+        "biomejs.biome",
+        "DavidAnson.vscode-markdownlint",
         "redhat.vscode-yaml",
         "ms-azuretools.vscode-containers",
         "github.vscode-github-actions"
       ],
       "settings": {
-        "typescript.preferences.quoteStyle": "single",
+        "editor.defaultFormatter": "biomejs.biome",
+        "editor.formatOnPaste": true,
         "editor.formatOnSave": true,
-        "editor.defaultFormatter": "esbenp.prettier-vscode",
-        "editor.codeActionsOnSave": {
-          "source.fixAll.eslint": "explicit"
+        "[css]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[graphql]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[html]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[javascript]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[javascriptreact]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[json]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[jsonc]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[markdown]": {
+          "editor.defaultFormatter": "DavidAnson.vscode-markdownlint"
         },
-        "files.exclude": {
-          "**/node_modules": true,
-          "**/target": true,
-          "**/.git": false
+        "[mdx]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[svelte]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[typescript]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[typescriptreact]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[vue]": {
+          "editor.defaultFormatter": "biomejs.biome"
+        },
+        "[yaml]": {
+          "editor.defaultFormatter": "redhat.vscode-yaml"
+        },
+        "editor.codeActionsOnSave": {
+          "source.fixAll.biome": "explicit",
+          "source.organizeImports.biome": "explicit"
         }
       }
     }

.github/PULL_REQUEST_TEMPLATE/bug_fix.md

@@ -23,7 +23,8 @@ labels: ['bug']
 
 ## Tests
 
-- [ ] Lint and type-check pass: `yarn lint`
+- [ ] Lint/format check passes: `yarn check`
+- [ ] Type-check passes: `yarn type-check`
 - [ ] Added/updated tests (if any)
 - [ ] Manual verification steps listed below
 

.github/PULL_REQUEST_TEMPLATE/feature.md

@@ -21,7 +21,8 @@ labels: ['enhancement']
 
 ## Tests
 
-- [ ] Lint and type-check: `yarn lint`
+- [ ] Lint/format check: `yarn check`
+- [ ] Type-check: `yarn type-check`
 - [ ] Build: `yarn compile`
 - [ ] Manual run: `yarn dev`
 - [ ] Screenshots or logs (if applicable)

.github/PULL_REQUEST_TEMPLATE/refactor.md

@@ -15,7 +15,8 @@ labels: ['refactor']
 
 ## Tests
 
-- [ ] Lint and type-check: `yarn lint`
+- [ ] Lint/format check: `yarn check`
+- [ ] Type-check: `yarn type-check`
 - [ ] Build: `yarn compile`
 - [ ] Manual smoke test (list):