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, 30 insertions, 0 deletions

diff --git a/src/features/workspaces/logic/view-model.ts b/src/features/workspaces/logic/view-model.ts
index 6dd64c6..b994b7c 100644
--- a/src/features/workspaces/logic/view-model.ts
+++ b/src/features/workspaces/logic/view-model.ts
@@ -20,6 +20,36 @@ export function pageTitle(route: Route, workspaces: readonly WorkspaceEntry[]):
 }
 
 /**
+ * Sort workspaces for display: starred first, then most-recently-active. Pure:
+ * the list in, a NEW sorted array out (the input is not mutated). Starred
+ * workspaces jump to the top (the FE-side echo of their concurrency-priority);
+ * within each group (starred / not) `lastActivityAt` desc breaks ties, matching
+ * the backend's list ordering. Stable for equal `lastActivityAt`.
+ */
+export function sortWorkspaces<T extends WorkspaceEntry>(workspaces: readonly T[]): T[] {
+  return [...workspaces].sort((a, b) => {
+    if (a.starred !== b.starred) return a.starred ? -1 : 1;
+    return b.lastActivityAt - a.lastActivityAt;
+  });
+}
+
+/**
+ * Return a NEW list with the one workspace's `starred` flag set (immutably —
+ * the entry is replaced, the rest keep their identity). Pure: the optimistic
+ * star/unstar transformation shared by the apply + the error revert. A missing
+ * `id` (not yet in the list — e.g. starring a workspace the home view hasn't
+ * loaded) leaves the list unchanged; the backend's create-on-miss still applies
+ * server-side and a subsequent refresh reconciles.
+ */
+export function applyStarred<T extends WorkspaceEntry>(
+  workspaces: readonly T[],
+  id: string,
+  starred: boolean,
+): T[] {
+  return workspaces.map((w) => (w.id === id ? { ...w, starred } : w));
+}
+
+/**
  * Format an epoch-ms timestamp as a short relative string ("now", "3m", "2h",
  * "5d", or a date). Pure: `now` + `then` in, string out. Future timestamps
  * (a workspace just created) read as "now".