refactor(app): reshape session store reads around narrow hook surface

Eliminate sidebar re-render cascades by fixing both sides of the
subscription contract:

- Session-store writes preserve identity: setWorkspaces, mergeWorkspaces,
  removeWorkspace, and patchWorkspaceScripts return the previous Map/entry
  reference when content is unchanged.
- HostRuntimeController.updateSnapshot only notifies when a patched field
  actually changed; idle probe ticks no longer replace the snapshot.
- New canonical hook surface in stores/session-store-hooks.ts
  (useWorkspace, useWorkspaceFields, useWorkspaceStructure,
  useWorkspaceKeys, useResolveWorkspaceIdByCwd,
  useWorkspaceStatusesForBadges, useWorkspaceExecutionAuthority,
  useRecommendedProjectPaths, useHasWorkspaces). These are the only
  place to subscribe to workspaces.
- 15 greedy subscribers migrated to the hook surface. The sidebar is now
  driven by useWorkspaceStructure for identity/ordering; each row
  hydrates its own descriptor via useWorkspaceFields, so a workspace
  update re-renders only its row. Archive-redirect callbacks switched to
  event-time useSessionStore.getState().
- Deleted dead code: use-session-directory.ts, workspace-fetch-debug.ts,
  and the unused SidebarProjectEntry aggregates (activeCount,
  totalWorkspaces, aggregated statusBucket).

No user-visible behavior change. Targeted tests green (79 tests across
host-runtime, session-store, session-store-hooks, sidebar list, sidebar
row model, sidebar shortcuts, workspace source of truth).

packages/app/src/components/project-picker-modal.tsx

@@ -6,7 +6,7 @@ import { useQuery } from "@tanstack/react-query";
 import { usePathname } from "expo-router";
 import { useKeyboardShortcutsStore } from "@/stores/keyboard-shortcuts-store";
 import { shortenPath } from "@/utils/shorten-path";
-import { useSessionStore } from "@/stores/session-store";
+import { useRecommendedProjectPaths } from "@/stores/session-store-hooks";
 import { useHosts, useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 import { useOpenProject } from "@/hooks/use-open-project";
 import { parseServerIdFromPathname } from "@/utils/host-routes";
@@ -29,9 +29,7 @@ export function ProjectPickerModal() {
 
   const client = useHostRuntimeClient(serverId ?? "");
   const isConnected = useHostRuntimeIsConnected(serverId ?? "");
-  const workspaces = useSessionStore((state) =>
-    serverId ? state.sessions[serverId]?.workspaces : undefined,
-  );
+  const recommendedPaths = useRecommendedProjectPaths(serverId);
 
   const inputRef = useRef<TextInput>(null);
   const [query, setQuery] = useState("");
@@ -39,13 +37,6 @@ export function ProjectPickerModal() {
   const [isSubmitting, setIsSubmitting] = useState(false);
   const openProject = useOpenProject(serverId);
 
-  const recommendedPaths = useMemo(() => {
-    if (!workspaces) return [];
-    return Array.from(workspaces.values())
-      .map((workspace) => workspace.projectRootPath)
-      .filter((path) => path.length > 0);
-  }, [workspaces]);
-
   const directorySuggestionsQuery = useQuery({
     queryKey: ["project-picker-directory-suggestions", serverId, query],
     queryFn: async () => {