Make workspace IDs opaque, independent of the filesystem path (#1503)

* Make workspace IDs opaque, independent of the filesystem path

Workspace IDs were the resolved checkout/worktree path, so code could
treat an ID as a path: prefix matching, deriving directories from it,
falling back to a path when a lookup missed. IDs are now opaque -
compared only by exact equality and never used as a path. Anything
path-shaped resolves the workspace record first and reads its cwd.

New workspaces get a generated `wks_` ID; existing path-shaped IDs are
read from disk and never regenerated, so there is no migration and no
change to the wire or persisted schemas. Groundwork for running
multiple workspaces in a single directory.

* Keep attachment scope key stable and align refetch test

The attachment scope key keeps `workspace=` instead of `wsid=` so existing
persisted drafts are not orphaned; the rename was cosmetic. The SDK refetch
test no longer asserts a filter, matching refetch fetching one page and
selecting by id client-side.

* Fix live agent updates in directories without a registered workspace

The opaque-ID work removed buildProjectPlacementForCwd's directory
fallback, so an agent running in a folder with no registered workspace
(e.g. a fresh non-git dir) produced a null placement. forwardAgentUpdate
then threw "Workspace not found", the error was swallowed by its catch,
and no agent_update was emitted — live model/thinking switches and status
updates silently stopped. Caught by the live-preferences e2e suite.

The fallback builds a directory-scoped project placement keyed by the
path. That key is a project grouping key (non-git projects group by
path), not a workspace id, so it stays within the opaque-id rule.

* Always run server worktree archive, even without a resolved workspace

Archiving bailed out entirely when the workspace was not found in the
client store, so a race or stale state could make "archive" do nothing
server-side with only a console.warn. The server archive is keyed by
worktreePath, which is always available, so it now runs regardless; only
the optimistic client-side updates (keyed by workspace id) are gated on
the workspace being resolved.

* Expect a directory-scoped placement for unregistered agent dirs

This unit test asserted the no-placement behavior reverted in the live
agent-update fix, which had broken live model/thinking switching. Update
it to expect the directory-scoped placement now emitted for an agent in a
directory with no registered workspace.

* Fix opaque workspace routing in app E2E

* Preserve workspace IDs during partial bootstrap

* Fix archive flows for opaque workspace IDs

* Stop treating opaque workspace IDs as filesystem paths

Workspace IDs are opaque (wks_<hex>), but several call sites still passed
the id where a directory was expected, which broke those flows for opaque
IDs. The branch switcher sent the id as a cwd to branch/stash/checkout git
operations, and server archive/reconcile cleanup keyed git-watch and
subscription teardown by id, leaking that state.

Git and filesystem operations now take the workspace directory; the opaque
id is used only for identity and cache keys. Archive/reconcile cleanup
routes through a single teardownArchivedWorkspace helper that keeps the key
split explicit: runtime store by id, git watch and subscription by cwd.
Path-derived grouping keys are renamed to directory keys, and the helpers
are split into workspace-identity and workspace-directory so the id-vs-path
boundary is obvious.

packages/app/src/stores/session-store-hooks/selectors.test.ts

@@ -8,7 +8,7 @@ import {
   selectRecommendedProjectPaths,
   selectResolveWorkspaceIdByCwd,
   selectWorkspace,
-  selectWorkspaceExecutionAuthority,
+  selectWorkspaceDirectory,
   selectWorkspaceFields,
   selectWorkspaceKeys,
   selectWorkspaceOrderByScopeForServer,
@@ -142,34 +142,30 @@ describe("selectWorkspace", () => {
   });
 });
 
-describe("selectWorkspaceExecutionAuthority", () => {
-  it("preserves the old missing-workspace message with the requested id", () => {
+describe("selectWorkspaceDirectory", () => {
+  it("returns the workspace directory, never the opaque workspace id", () => {
+    const workspace = createWorkspace({
+      id: "wks_3f9a2b1c",
+      workspaceDirectory: "/Users/dev/project",
+    });
+    initializeWorkspaces([workspace]);
+
+    const directory = selectWorkspaceDirectory(
+      useSessionStore.getState(),
+      SERVER_ID,
+      "wks_3f9a2b1c",
+    );
+
+    expect(directory).toBe("/Users/dev/project");
+    expect(directory).not.toBe("wks_3f9a2b1c");
+  });
+
+  it("returns null when the workspace is missing", () => {
     initializeWorkspaces([]);
 
     expect(
-      selectWorkspaceExecutionAuthority(useSessionStore.getState(), SERVER_ID, "missing-id"),
-    ).toMatchObject({
-      ok: false,
-      message: "Workspace not found: missing-id",
-    });
-  });
-
-  it("keeps deep-equal authority references under unrelated workspace updates", () => {
-    const workspaceA = createWorkspace({ id: "workspace-a", name: "A" });
-    const workspaceB = createWorkspace({ id: "workspace-b", name: "B" });
-    initializeWorkspaces([workspaceA, workspaceB]);
-
-    const tracked = trackSelector(
-      useSessionStore,
-      (state) => selectWorkspaceExecutionAuthority(state, SERVER_ID, workspaceA.id),
-      workspaceEqualityFns.deep,
-    );
-    const before = tracked.current;
-
-    useSessionStore.getState().mergeWorkspaces(SERVER_ID, [{ ...workspaceB, status: "running" }]);
-    expect(tracked.current).toBe(before);
-
-    tracked.stop();
+      selectWorkspaceDirectory(useSessionStore.getState(), SERVER_ID, "missing-id"),
+    ).toBeNull();
   });
 });