perf(browser-search): index hot query path

[JustYannicc]

What changed

• Added token-prefix, trigram, per-entry search, and bookmark nickname lookup data to the browser entry index.
• Routed bookmark/history query candidate selection through indexed entry ID intersections, then kept the existing scoring and ordering checks as the source of truth.
• Added a real synthetic browser search performance harness covering 24k history/bookmark rows, 300 tabs, nickname matches, full-scan parity, and generous query thresholds.

Why

Browser search was still scanning every history and bookmark entry for typed root queries even though an entry index existed. Large browser datasets could make each keystroke spend more than 100 ms in candidate generation.

Compatibility impact

Search result scoring, dedupe, completion, and ordering are preserved by verifying indexed candidates with the existing full scoring path. The code falls back to full scans when the query shape cannot be represented safely by the index. No user-facing strings or i18n keys changed.

How tested

• Baseline before editing on synthetic 24,000 entries and 300 tabs: ranked avg 150.94-199.77 ms; ordered avg 173.56-224.59 ms.
• Final harness on synthetic 24,001 entries and 300 tabs: index build 300.50 ms; ranked full-scan avg 133.60-160.05 ms; ranked indexed avg 1.44-14.03 ms; ordered full-scan avg 134.62-154.54 ms; ordered indexed avg 1.39-12.52 ms.
• node --test scripts/test-browser-search-lag-fix.mjs scripts/test-browser-search-performance.mjs
• node --test 'scripts/test-*.mjs'
• ./node_modules/.bin/tsc -p tsconfig.main.json
• ./node_modules/.bin/vite build
• node scripts/check-i18n.mjs
• Codex LSP diagnostics for src/renderer/src/hooks/useBrowserSearch.ts: no errors.

Stack validation

This issue was found and validated from codex/perf-integration-stack, which contains the current performance fix stack, including the renderer typecheck cleanup from #518. On that integrated branch, ./node_modules/.bin/tsc -p tsconfig.renderer.json --noEmit --pretty false, ./node_modules/.bin/tsc -p tsconfig.main.json --noEmit --pretty false, and node --test 'scripts/test-*.mjs' pass.

[JustYannicc]

Superseded by the consolidated upstream PR #535: #535