refactor(shared-ui): extract search-core for highlight + debounce

Both QuickInputBar (InputBar.svelte), CommandBar.svelte, and GlobalSpotlight
were duplicating syntax highlighting and the 150ms search debounce. Pull
these into a new `packages/shared-ui/src/search-core/` module so the two
input surfaces stay in sync on feel and matching rules.

- search-core/highlight.ts — HighlightPattern type, locale-aware
  getHighlightPatterns(), and the shared highlightText() (HTML-escape +
  span wrap). Patterns were previously in quick-input/highlightPatterns.ts
  + inline in CommandBar.svelte.
- search-core/config.ts — SEARCH_DEBOUNCE_MS = 150. Used from InputBar,
  CommandBar, GlobalSpotlight, and apps/mana web SearchEngine.
- quick-input/highlightPatterns.ts + types.ts become thin back-compat
  re-exports.
- Public surface: @mana/shared-ui now exports getHighlightPatterns,
  highlightText, SEARCH_DEBOUNCE_MS, and the HighlightPattern type.

No UX change. UIs still live in their own files (per earlier split
recommendation: shared backend, separate surfaces).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/mana/apps/web/src/lib/search/engine.svelte.ts

@@ -6,8 +6,7 @@
 
 import { SearchRegistry } from './registry';
 import type { GroupedSearchResults } from './types';
-
-const DEBOUNCE_MS = 150;
+import { SEARCH_DEBOUNCE_MS as DEBOUNCE_MS } from '@mana/shared-ui';
 
 export function createSearchEngine() {
 	const registry = new SearchRegistry();