[kvnloo]

What Changed

useLocalStorage's setValue no longer reads and decodes the current stored value before a plain-value write — plain values never needed the old blob. Updater-function writes still read it, but now fall back to the initial value on decode failure (matching the read path) instead of turning the write into a silent no-op.

Why

setValue always decoded the stored blob first; a JSON-valid but schema-invalid blob (truncated write from a crash, a schema that gained a required field, a value written by a different build shape) made decode throw, and the catch only logged it. Every later setter call on that key was a silent no-op while the read path kept showing the initial value — an internally inconsistent fail-open/fail-closed split. User-visible: provider-update dismissals, resume-compaction dismissal, sidebar shelf state, and diff-panel file-tree state would snap back and never persist until site storage was cleared manually.

Validation

• 3 new behavior tests (useLocalStorage.setValue.test.tsx): plain write heals a corrupt blob; updater runs against the initial value on a corrupt blob; normal write/updater paths unchanged.
• Red on base: the 2 corrupt-blob tests fail on base, the normal-path test passes on both.
• Existing useLocalStorage.test.ts 6/6 green; apps/web tsc --noEmit clean; vp fmt --check clean.

Checklist

• This PR is small and focused
• I explained what changed and why
• No UI changes

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Authored with AI assistance (Muse, Meta's Muse Spark) under the contributor's direction.