refactor: extract shared command palette, inline file tree editing, surgical SQLite index sync

[braden-w]

Extracts a shared CommandPalette component into packages/ui, replaces opensidian's modal file dialogs with inline tree inputs, and swaps the SQLite index extension's full nuke-and-rebuild with surgical per-row syncing.

Both opensidian and tab-manager had their own command palette implementations with duplicated logic—filtering, grouping, keyboard navigation. This PR unifies them behind a single CommandPaletteItem[] contract so apps just provide data:

// Any app can feed the shared palette with this shape
export const items: CommandPaletteItem[] = [
  {
    id: 'dedup',
    label: 'Remove Duplicates',
    icon: CopyMinusIcon,
    keywords: ['dedup', 'duplicate', 'remove'],
    group: 'Quick Actions',
    onSelect() { /* ... */ },
  },
];

The keywords field uses bits-ui's native keywords prop for independent scoring instead of concatenating into value. Tab-manager's palette items moved from a disconnected quick-actions.ts into components/command-palette/items.ts, co-located next to the component. The commandsFromActions bridge in workspace was deleted—it was dead code (every tab-manager action requires input, so the default filter produced zero items).

┌──────────────────────────────────────────────────┐
│  Before: each app builds its own palette         │
│                                                  │
│  opensidian/CommandPalette.svelte  ──┐           │
│  tab-manager/CommandPalette.svelte ──┤ duplicate │
│                                      │ logic     │
│  (filtering, grouping, keyboard)   ──┘           │
├──────────────────────────────────────────────────┤
│  After: shared component, apps provide data      │
│                                                  │
│  packages/ui/CommandPalette ◀── CommandPaletteItem[]
│    ├── opensidian: palette items                 │
│    └── tab-manager: palette items                │
└──────────────────────────────────────────────────┘

Opensidian's CreateDialog and RenameDialog modals felt disconnected from the tree—every major file explorer (VS Code, Obsidian, JetBrains) uses inline inputs at the insertion point instead. The new InlineNameInput renders directly in the tree with Enter/Escape/blur handling, auto-focus, and stem-only selection. Keyboard shortcuts (N, ⇧N, F2, Delete) are now scoped to the tree. Net result: -1 component, -8 lines, better UX.

The SQLite index extension previously nuked and rebuilt the entire database on every Y.Doc change—fine for a dozen files, unusable past a few hundred. Now syncRows() processes only the changed IDs accumulated across a debounce window, with folder renames cascading to descendants via LIKE query. rebuild() is preserved for initial load only.

// Before: every Yjs mutation triggers full rebuild
doc.on('update', () => rebuildEntireIndex(doc));

// After: debounced sync of only changed rows
doc.on('update', () => scheduleSync(changedIds));
// syncRows() does per-row upserts/deletes based on changedIds

Also in this PR: lucide-svelte → @lucide/svelte migration for Svelte 5 compatibility in opensidian, consistent appendFile option forwarding in the filesystem package, and describe-workspace now exports actions for introspection.