docs(persist): clarify createJSONStorage behavior and warn about production use

[Copilot]

#3540

createJSONStorage is widely used in examples but lacks type safety and runtime validation — data read from storage is blindly cast to the state type, so corrupt or stale values are silently accepted. No warning about this existed in the docs.

Summary

• storage option description — expanded to explain the lazy getter pattern (SSR safety) and added an inline warning that createJSONStorage does not validate the deserialized shape; recommends a custom PersistStorage with schema validation (e.g. Zod) for production use.
• "Persisting a state with custom storage" section — added a note at the top of the section reinforcing the same point: createJSONStorage is suited for prototyping, not production.

Check List

• pnpm run fix for formatting and linting code and docs

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Project	Deployment	Actions	Updated (UTC)
zustand-demo	Ready	Preview, Comment	Jul 9, 2026 9:35pm

[github-actions]

Size Change: 0 B

Total Size: 13.1 kB

ℹ️ View Unchanged

Filename	Size
dist/esm/index.mjs	64 B
dist/esm/middleware.mjs	4.1 kB
dist/esm/middleware/immer.mjs	212 B
dist/esm/react.mjs	342 B
dist/esm/react/shallow.mjs	198 B
dist/esm/shallow.mjs	82 B
dist/esm/traditional.mjs	412 B
dist/esm/vanilla.mjs	405 B
dist/esm/vanilla/shallow.mjs	557 B
dist/index.js	244 B
dist/middleware.js	4.11 kB
dist/middleware/immer.js	231 B
dist/react.js	357 B
dist/react/shallow.js	213 B
dist/shallow.js	189 B
dist/traditional.js	426 B
dist/vanilla.js	418 B
dist/vanilla/shallow.js	568 B

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[pkg-pr-new]

• demo

• starter

  npm i https://pkg.pr.new/zustand@3541
  

commit: 2c6a0bf