Refactor: Fine-Grained Reactive Data Context

CHANGELOG.md

@@ -39,7 +39,7 @@ xx.xx.xxxx
 ### Utils
 * **Feature** - Added [`deepFreeze`](https://next.semantic-ui.com/docs/api/utils/cloning#deepfreeze) — recursively freezes a value in place and returns the same reference. Walks arrays and plain objects only, leaving `Date`, `Map`, `Set`, `RegExp`, DOM nodes, and custom class instances untouched so their internal slots keep working. Cycle-safe via an internal `WeakSet`; already-frozen inputs take a fast-path no-op.
 * **Feature** - Added [`createCache`](https://next.semantic-ui.com/docs/api/utils/cache) — a bounded, Map-like cache factory with pluggable eviction (`lru` default, `fifo`, `flush`) and an `onEvict` hook. Collapses ad-hoc `new Map()` + size-check patterns behind one named primitive.
-* **Feature** - Added `assignInPlace()` for syncing an object's contents to match a source without replacing the reference — supports `preserveExistingKeys` to skip deletion and `returnChanged` to detect modifications
+* **Feature** - Added `assignInPlace()` for syncing an object's contents to match a source without replacing the reference — supports `preserveExistingKeys` to skip deletion, `preserveGetters` to keep computed properties (own getter descriptors) intact across syncs, and `returnChanged` to detect modifications
 * **Breaking** - `kebabToCamel` and `camelToKebab` now use lossless encoding — digit-leading segments are preserved with `_` (e.g. `grid-2x2` → `grid_2x2`), and every uppercase letter gets its own hyphen (e.g. `arrowDownAZ` → `arrow-down-a-z`). Both accept a `separator` option to customize the digit-boundary character. `camelToKebab` now normalizes leading uppercase by default for DOM-safe output (e.g. `FooBar` → `foo-bar`); pass `{ lossless: true }` to preserve it for exact round-trips.
 * **Enhancement** - `hashCode` now defaults to zero-allocation FNV-1a for better performance. Use `{ fast: false }` for the previous UMASH algorithm with stronger collision resistance.
 * **Feature** - Added `unescapeHTML()` for converting HTML entities back to characters — the inverse of `escapeHTML`

ai/plans/ROADMAP.md

@@ -83,6 +83,7 @@ Plans with an open PR or live pair work. Updated as ceremony when a PR opens; en
 
 - [Release 0.18.0](active/release-0-18-0.md) — [PR #122](https://github.com/Semantic-Org/Semantic-Next/pull/122) `docs/shippable` (menu trimming + audit pass pending). Ships the next tagged release; last was 0.17.0 in November.
 - [Signal Performance](active/signal-performance.md) — [PR #150](https://github.com/Semantic-Org/Semantic-Next/pull/150) freeze-by-default. Perf story unresolved (see plan's Bench Results); release inclusion is the open call.
+- [Fine-Grained Reactivity](active/fine-grained-reactivity.md) — [PR #183](https://github.com/Semantic-Org/Semantic-Next/pull/183) `ReactiveDataContext` per-key Signal bag. Session 1 (each-block) landed; subtemplate, snippet, hydration sites still pending.
 ---
 
 ## Phase 0 — Renderer Architecture
@@ -110,7 +111,7 @@ Behavioral changes and API contracts that downstream agents and consumers will t
 | # | Plan | Hours | Mode | Scope | Notes |
 |---|------|-------|------|-------|-------|
 | 2a | [Signal Performance](active/signal-performance.md) | 4-5h + audit | pair | scoped | `safety` preset system (`freeze` / `reference` / `none`) replacing `allowClone`. Audit of `.get()` call sites for get-mutate-set patterns gates the default flip. |
-| 2a.1 | [Fine-Grained Reactivity](fine-grained-reactivity.md) | 6-8h | pair | initial | `ReactiveDataContext` — per-key Signal bag — at `{#each}` items, subtemplate `reactiveData`, snippet args. Eliminates the N×M coarse invalidation pattern. Lands after 2a. |
+| 2a.1 | [Fine-Grained Reactivity](active/fine-grained-reactivity.md) | 6-8h | pair | initial | `ReactiveDataContext` — per-key Signal bag — at `{#each}` items, subtemplate `reactiveData`, snippet args. Eliminates the N×M coarse invalidation pattern. Lands after 2a. |
 | 2b | [Value Schema](value-schema.md) | 16-24h (2-3d) | pair | initial | Contract for ~20-30 form components. `value` setting + schema + `change` event. Gates form/form-field and the wrapper architecture. |
 | 2c | [State from Settings](state-from-settings.md) | 8h | pair | scoped | `{ default: 'all', from: 'setting' }` in `defaultState`. Eliminates manual shadowing for components that accept initial values from attributes but own them as state. |
 | 2d | [Subtemplate Settings](subtemplate-settings.md) | 8-12h | pair | initial | Reactive `defaultSettings` on subtemplates with merged proxy over parent web component settings. Same upgrade path: add `tagName` and the subtemplate becomes a web component with no API change. |