feat(workstate): UI live-state des conversations/délégations (Lot A frontend)

Ajoute le port et l'adaptateur workState (+ mock) côté frontend, le type domaine
associé, et la feature `workstate` (panneau ProjectWorkStatePanel + hook
useProjectWorkState) consommant le read-model live exposé par le backend.
Intègre le panneau dans ProjectsView. Tests verts (workstate + projects).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/ports/index.ts

@@ -33,6 +33,7 @@ import type {
   PermissionSet,
   Project,
   ProjectPermissions,
+  ProjectWorkState,
   ProfileAvailability,
   ResumableAgent,
   Skill,
@@ -639,6 +640,12 @@ export interface PermissionGateway {
   ): Promise<EffectivePermissions | null>;
 }
 
+/** Read-only live work-state read-model for conversations/delegations. */
+export interface WorkStateGateway {
+  /** Reads the current per-agent live/offline and idle/busy state for a project. */
+  getProjectWorkState(projectId: string): Promise<ProjectWorkState>;
+}
+
 /**
  * The full set of gateways the app depends on, injected via the DI provider.
  * The composition (real vs mock) is chosen in `app/`.
@@ -658,4 +665,5 @@ export interface Gateways {
   memory: MemoryGateway;
   embedder: EmbedderGateway;
   permission: PermissionGateway;
+  workState: WorkStateGateway;
 }