feat(workspaces): star toggle for concurrency priority

Backend (feature/workspace-star) shipped Workspace.starred: boolean (additive
to [email protected], no version bump) + PUT/DELETE /workspaces/:id/star endpoints
(no body; create-on-miss; return the updated Workspace). A starred workspace's
agents jump ahead of non-starred ones in the concurrency limiter queue
(oldest-agent-first within each group); takes effect immediately for
already-queued agents.

FE consumed:
- adapter/http.ts: star(id)/unstar(id) -> WorkspaceResult<Workspace>
  (PUT/DELETE /workspaces/:id/star, no body).
- logic/view-model.ts: pure sortWorkspaces (starred-first, then lastActivityAt
  desc, stable) + pure applyStarred (the optimistic apply/revert transform).
- store.svelte.ts: setStarred(id, starred) — optimistic flip with error revert;
  the list is now a $derived sorted view (starred bubble to top reactively);
  no full refresh on success (avoids flicker).
- ui/WorkspaceCard.svelte: star toggle button (filled gold when starred,
  outline when not; spinner in flight; aria-pressed/aria-label; tooltip notes
  concurrency priority).
- Re-mirrored .dispatch/wire.reference.md (starred + delta note).
- GLOSSARY.md: 'starred' term.

Tests (+27): http star/unstar (5), view-model sort+applyStarred (12), store
optimistic+revert+re-sort (6), WorkspaceCard star button (4).

Verification: typecheck 0/0, 1045 tests green, biome clean, build OK.
backend-handoff.md updated (workspace-star slice, no open backend asks).

1 files changed, 108 insertions, 0 deletions

diff --git a/src/features/workspaces/ui/WorkspaceCard.test.ts b/src/features/workspaces/ui/WorkspaceCard.test.ts
index 0d03b8e..f3ed1e7 100644
--- a/src/features/workspaces/ui/WorkspaceCard.test.ts
+++ b/src/features/workspaces/ui/WorkspaceCard.test.ts
@@ -12,6 +12,7 @@ function fakeEntry(overrides: Partial<WorkspaceEntry> = {}): WorkspaceEntry {
     title: "My Workspace",
     defaultCwd: null,
     defaultComputerId: null,
+    starred: false,
     createdAt: 1,
     lastActivityAt: 2,
     conversationCount: 3,
@@ -40,6 +41,12 @@ function fakeStore() {
         value: fakeEntry({ id, defaultComputerId: computerId }),
       }),
     ),
+    setStarred: vi.fn(
+      async (id: string, starred: boolean): Promise<WorkspaceResult<WorkspaceEntry>> => ({
+        ok: true,
+        value: fakeEntry({ id, starred }),
+      }),
+    ),
     remove: vi.fn(
       async (): Promise<WorkspaceResult<{ closedCount: number }>> => ({
         ok: true,
@@ -135,4 +142,105 @@ describe("WorkspaceCard", () => {
     expect(onNavigate).toHaveBeenCalledTimes(1);
     expect(onNavigate).toHaveBeenCalledWith("/my-ws");
   });
+
+  it("renders an outline star button for an unstarred workspace", () => {
+    const store = fakeStore() as unknown as WorkspaceStore;
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+    const star = screen.getByRole("button", { name: "Star workspace" });
+    expect(star).toHaveAttribute("aria-pressed", "false");
+  });
+
+  it("renders a filled star button for a starred workspace", () => {
+    const store = fakeStore() as unknown as WorkspaceStore;
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: true }), store, onNavigate: vi.fn(), computers: [] },
+    });
+    const star = screen.getByRole("button", { name: "Unstar workspace" });
+    expect(star).toHaveAttribute("aria-pressed", "true");
+  });
+
+  it("toggles the star via the store on click", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    await user.click(screen.getByRole("button", { name: "Star workspace" }));
+    expect(store.setStarred).toHaveBeenCalledWith("my-ws", true);
+  });
+
+  it("clicking a starred workspace's star calls setStarred(id, false)", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: true }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    await user.click(screen.getByRole("button", { name: "Unstar workspace" }));
+    expect(store.setStarred).toHaveBeenCalledWith("my-ws", false);
+  });
+
+  it("renders no star error on a successful toggle", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    await user.click(screen.getByRole("button", { name: "Star workspace" }));
+    expect(screen.queryByText(/Star toggle failed/i)).not.toBeInTheDocument();
+  });
+
+  it("shows an inline error when setStarred fails (result.ok false)", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    // The store reverts the optimistic flip on failure, so the entry's
+    // `starred` stays false — fake the revert by returning ok:false unchanged.
+    store.setStarred = vi.fn(
+      async (): Promise<WorkspaceResult<WorkspaceEntry>> => ({ ok: false, error: "boom" }),
+    );
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    await user.click(screen.getByRole("button", { name: "Star workspace" }));
+
+    expect(screen.getByText("boom")).toBeInTheDocument();
+  });
+
+  it("re-enables the star button after a failure (savingStar resets)", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    store.setStarred = vi.fn(
+      async (): Promise<WorkspaceResult<WorkspaceEntry>> => ({ ok: false, error: "boom" }),
+    );
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    const star = screen.getByRole("button", { name: "Star workspace" });
+    await user.click(star);
+    // After the failed toggle, the button is NOT disabled (savingStar reset).
+    expect(star).not.toBeDisabled();
+  });
+
+  it("re-enables the star button even when setStarred throws", async () => {
+    const user = userEvent.setup();
+    const store = fakeStore() as unknown as WorkspaceStore;
+    store.setStarred = vi.fn(async (): Promise<WorkspaceResult<WorkspaceEntry>> => {
+      throw new Error("network");
+    });
+    render(WorkspaceCard, {
+      props: { ws: fakeEntry({ starred: false }), store, onNavigate: vi.fn(), computers: [] },
+    });
+
+    const star = screen.getByRole("button", { name: "Star workspace" });
+    await user.click(star);
+    // savingStar must reset via try/finally even on a throw.
+    expect(star).not.toBeDisabled();
+    expect(screen.getByText("network")).toBeInTheDocument();
+  });
 });