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).

2 files changed, 86 insertions, 0 deletions

diff --git a/src/features/workspaces/adapter/http.test.ts b/src/features/workspaces/adapter/http.test.ts
index 19e53f8..18d8939 100644
--- a/src/features/workspaces/adapter/http.test.ts
+++ b/src/features/workspaces/adapter/http.test.ts
@@ -130,4 +130,60 @@ describe("createWorkspaceHttp", () => {
     const result = await http.delete("default");
     expect(result).toEqual({ ok: false, error: "cannot delete default" });
   });
+
+  it("star PUTs /star with no body and returns the updated workspace", async () => {
+    const ws = {
+      id: "a",
+      title: "A",
+      defaultCwd: null,
+      defaultComputerId: null,
+      starred: true,
+      createdAt: 1,
+      lastActivityAt: 2,
+    };
+    const fetchImpl = fakeFetch([{ body: ws }]);
+    const http = createWorkspaceHttp(BASE, fetchImpl);
+    const result = await http.star("a");
+    expect(result).toEqual({ ok: true, value: ws });
+    const call = (fetchImpl as unknown as ReturnType<typeof vi.fn>).mock.calls[0];
+    expect(call?.[0]).toBe(`${BASE}/workspaces/a/star`);
+    expect(call?.[1]).toEqual({ method: "PUT" });
+  });
+
+  it("unstar DELETEs /star with no body and returns the updated workspace", async () => {
+    const ws = {
+      id: "a",
+      title: "A",
+      defaultCwd: null,
+      defaultComputerId: null,
+      starred: false,
+      createdAt: 1,
+      lastActivityAt: 2,
+    };
+    const fetchImpl = fakeFetch([{ body: ws }]);
+    const http = createWorkspaceHttp(BASE, fetchImpl);
+    const result = await http.unstar("a");
+    expect(result).toEqual({ ok: true, value: ws });
+    const call = (fetchImpl as unknown as ReturnType<typeof vi.fn>).mock.calls[0];
+    expect(call?.[0]).toBe(`${BASE}/workspaces/a/star`);
+    expect(call?.[1]).toEqual({ method: "DELETE" });
+  });
+
+  it("star surfaces a 400 for an invalid slug", async () => {
+    const http = createWorkspaceHttp(
+      BASE,
+      fakeFetch([{ status: 400, body: { error: "invalid slug" } }]),
+    );
+    const result = await http.star("UPPER");
+    expect(result).toEqual({ ok: false, error: "invalid slug" });
+  });
+
+  it("unstar surfaces the backend error on failure", async () => {
+    const http = createWorkspaceHttp(
+      BASE,
+      fakeFetch([{ status: 500, body: { error: "Failed to unstar workspace" } }]),
+    );
+    const result = await http.unstar("a");
+    expect(result).toEqual({ ok: false, error: "Failed to unstar workspace" });
+  });
 });
diff --git a/src/features/workspaces/adapter/http.ts b/src/features/workspaces/adapter/http.ts
index 01fe677..5673881 100644
--- a/src/features/workspaces/adapter/http.ts
+++ b/src/features/workspaces/adapter/http.ts
@@ -25,6 +25,8 @@ import type {
  * - `PUT /workspaces/:id/title` → rename
  * - `PUT /workspaces/:id/default-cwd` → set/clear default cwd
  * - `PUT /workspaces/:id/default-computer` → set/clear default computer (SSH handoff #2)
+ * - `PUT /workspaces/:id/star` (create-on-miss) → star (concurrency priority)
+ * - `DELETE /workspaces/:id/star` (create-on-miss) → unstar
  * - `DELETE /workspaces/:id` (409 for "default") → delete
  */
 export type WorkspaceResult<T> =
@@ -38,6 +40,10 @@ export interface WorkspaceHttp {
   setTitle(id: string, title: string): Promise<WorkspaceResult<Workspace>>;
   setDefaultCwd(id: string, defaultCwd: string | null): Promise<WorkspaceResult<Workspace>>;
   setDefaultComputer(id: string, computerId: string | null): Promise<WorkspaceResult<Workspace>>;
+  /** Star a workspace (concurrency priority). Create-on-miss; no body. */
+  star(id: string): Promise<WorkspaceResult<Workspace>>;
+  /** Unstar a workspace. Create-on-miss; no body. */
+  unstar(id: string): Promise<WorkspaceResult<Workspace>>;
   delete(id: string): Promise<WorkspaceResult<{ closedCount: number }>>;
 }
 
@@ -141,6 +147,30 @@ export function createWorkspaceHttp(httpBase: string, fetchImpl: typeof fetch):
       }
     },
 
+    async star(id): Promise<WorkspaceResult<Workspace>> {
+      try {
+        const res = await fetchImpl(`${httpBase}/workspaces/${encodeURIComponent(id)}/star`, {
+          method: "PUT",
+        });
+        if (!res.ok) return { ok: false, error: await errText(res) };
+        return { ok: true, value: (await res.json()) as WorkspaceResponse };
+      } catch (err) {
+        return { ok: false, error: err instanceof Error ? err.message : "Star failed" };
+      }
+    },
+
+    async unstar(id): Promise<WorkspaceResult<Workspace>> {
+      try {
+        const res = await fetchImpl(`${httpBase}/workspaces/${encodeURIComponent(id)}/star`, {
+          method: "DELETE",
+        });
+        if (!res.ok) return { ok: false, error: await errText(res) };
+        return { ok: true, value: (await res.json()) as WorkspaceResponse };
+      } catch (err) {
+        return { ok: false, error: err instanceof Error ? err.message : "Unstar failed" };
+      }
+    },
+
     async delete(id): Promise<WorkspaceResult<{ closedCount: number }>> {
       try {
         const res = await fetchImpl(`${httpBase}/workspaces/${encodeURIComponent(id)}`, {