feat(app): persist search history with a clickable recent-searches dropdown

[zengtianli]

Intro

This PR adds a persistent search history to the file-search bar: past queries are saved across app restarts and can be re-run with a single click from a small clock-icon dropdown next to the search options.

It builds directly on top of the in-memory ArrowUp/ArrowDown history from #31 rather than replacing it — see How it relates to #31 below.

What & why

The ArrowUp/ArrowDown history added in #31 is great for cycling through queries within a session, but it lives entirely in memory and disappears on restart, and it's only reachable via the keyboard. This PR complements it with:

• Persistence — queries survive an app restart (stored in localStorage under cardinal.recentSearches, newest-first, deduped, capped at 50 entries).
• Discoverability — a clock-icon toggle opens a dropdown listing recent queries; clicking one re-runs it immediately. Includes a "clear history" action, and closes on Esc or an outside click.
• Smarter recording — history is recorded not only when a query is submitted, but also when a result is actually opened (double-click, Cmd+O, or the context menu), on the reasoning that a search which led to an open is a search worth remembering.

Implementation

Key files:

File	Change
src/hooks/useRecentSearches.ts	New hook. Wraps the existing useStoredState to persist a newest-first, deduped, capped list; exposes recordSearch / clearRecentSearches. Trims blanks and ignores malformed persisted payloads.
src/utils/openResultPath.ts	Adds a tiny subscribeResultOpened pub/sub so any result-open path (double-click / Cmd+O / context menu) can notify subscribers without prop-drilling.
src/hooks/useFilesTabState.ts	New optional onQueryCommitted callback, fired when a query is submitted, so committed queries flow into history.
src/components/SearchBar.tsx	New history toggle button + dropdown panel (list, empty state, clear action), with Esc / outside-click handling and ARIA (aria-haspopup / aria-expanded on the toggle, labelled panel, native <button> semantics for entries). All strings are props.
src/App.tsx	Wires the hook to the SearchBar, subscribes to subscribeResultOpened, and passes i18n'd labels.
src/App.css	Styles for the toggle and panel, using the existing CSS variables so it themes correctly in light/dark.
src/i18n/resources/*.json	New search.history.{toggle,empty,clear} keys across all 15 locales.
src/hooks/__tests__/useRecentSearches.test.ts	6 unit tests (see Testing).

Notes:

• Reuses the existing useStoredState helper rather than hand-rolling storage access.
• The history UI is gated to the Files tab (historyEnabled) so it doesn't appear where it wouldn't make sense.
• Styling relies entirely on existing theme variables (--color-accent, --color-elevated-bg, etc.), so light/dark both work with no extra tokens.

How it relates to #31

This is complementary, not a replacement:

• feat: navigate search history using ArrowUp/ArrowDown #31 (useSearchHistory.ts) gives in-memory ArrowUp/ArrowDown cycling within a session — fast keyboard recall while you work.
• This PR persists queries to localStorage across sessions and surfaces them in a clickable dropdown — durable recall and mouse discoverability.

The two coexist: the keyboard history from #31 is untouched (a separate hook file), and this PR layers persistence + a visible UI on top.

Testing

Ran from cardinal/:

• npm run format:check — clean.
• npm run typecheck (tsc --noEmit) — clean, no type errors.
• npm test -- --run (vitest) — all green (278 passed), including 6 new unit tests for useRecentSearches covering: newest-first ordering + persistence, blank/whitespace trimming, dedup-to-front, cap at max entries, restore-on-mount + clear, and rejecting malformed persisted payloads.
• npm run build (vite) — succeeds.
• Built the Tauri app and manually verified end-to-end: ran several searches, opened results, confirmed the dropdown re-runs past queries, then restarted the app and confirmed history persisted.

No Rust was touched.

Screenshots

A screenshot / GIF of the dropdown in action can be added here on request.