perf(sidebar): index session ownership and narrow live subscriptions

Replace repeated project-by-session directory matching across sidebar hooks with a shared ownership index that resolves each unique directory once and exposes direct project and folder-scope buckets.

Gate destructive folder reconciliation on authoritative session data and topology readiness, preserve last-known worktrees after discovery failures, and retain nested-project, VS Code, active/archive dedupe, and Windows drive-root semantics.

Narrow cross-directory subscriptions to session and status slices so streaming deltas no longer trigger global aggregation. Reuse a cached session ID index for permission lineage checks instead of rebuilding it on every session switch.

On the reported 15-project, 67-worktree, 14,561-session shape, ownership indexing averages 3.81 ms versus roughly 450 ms for the cache-only hotfix.

Validation: 28 targeted tests, UI type-check, UI lint, and dead-code analysis.

packages/ui/src/stores/permissionStore.test.ts

@@ -4,7 +4,7 @@ let fetchImpl: (input: string, init?: RequestInit) => Promise<Response>;
 mock.module('@/lib/runtime-fetch', () => ({
   runtimeFetch: (input: string, init?: RequestInit) => fetchImpl(input, init),
 }));
-mock.module('@/sync/sync-refs', () => ({ getAllSyncSessions: () => [] }));
+mock.module('@/sync/sync-refs', () => ({ getAllSyncSessionMap: () => new Map() }));
 mock.module('@/sync/session-ui-store', () => ({
   useSessionUIStore: { getState: () => ({ getDirectoryForSession: () => '/project' }) },
 }));