perf(emoji): reuse inline picker matches while navigating

[JustYannicc]

What changed

• Added a module-level cache for the currently rendered inline emoji picker matches.
• Render refreshes the cache for each new query; hide clears it.
• Left/right navigation and enter/tab insertion now reuse the rendered match list instead of rescanning emoji data.
• Added a VM-based Node test harness for the inline emoji picker path without importing the full Electron main entrypoint.

Why

• The inline picker query does not change during arrow navigation, but the previous path searched emoji data in handleEmojiTriggerNav and again in updateEmojiPickerSelection for each left/right key.
• Reusing the rendered matches removes those repeated full scans while keeping the same ordered result list.

Compatibility impact

• Emoji ordering remains the static emoji-data.json search ordering produced during render.
• Excluded-app dismissal, picker hide/intercept behavior, zero-match hide, selection wraparound, enter/tab insertion, and escape dismissal are preserved.
• Cached matches are cleared on hide so stale query data is not reused after dismissal or insertion.

How tested

• node --test scripts/test-inline-emoji-picker-match-cache.mjs
• node --test 'scripts/test-*.mjs' (238 pass, 1 skip, 0 fail)
• ./node_modules/.bin/tsc -p tsconfig.main.json --pretty false
• Codex LSP diagnostics for src/main/main.ts: no error diagnostics; all-severity check showed only preexisting hint-level items outside this change.

Performance evidence

• Harness data: src/main/emoji-data.json with 1,870 entries, query smi, 500 repeated sequences of 20 right-arrow navigation steps.
• Legacy repeated-navigation search model: 20,000 search calls, 2,899.988 ms total, 5.8 ms per sequence.
• Cached model: 500 search calls, 76.143 ms total, 0.1523 ms per sequence.
• Search-call reduction: 40x, with matching checksum 113000; the VM path also asserts left/right/enter perform 0 additional searches after render.

Stack validation

• Started from fork/codex/perf-consolidated-integration-stack at 264fb89dc5c867d6c3d77bc4b95e26e235e326ea.
• Work branch: codex/perf-emoji-picker-match-cache.
• Commit: 2cbcf35 (perf(emoji): reuse inline picker matches while navigating).

Replaces

• None.

[JustYannicc]

Superseded by the consolidated wave-2 UI/runtime PR: #572