feat(agent): orchestration v3 — surface MCP model-agnostic (M0→M4) — §14.3

Expose l'orchestration IdeA comme serveur MCP par-dessus le même
OrchestratorService::dispatch, avec repli fichier .ideai/requests pour les
CLI sans MCP. v3 réduite à la surface MCP : la messagerie inter-agents et la
corrélation requête↔réponse étaient déjà résolues par §17 (send_blocking).

- M0 capacité MCP sur le profil (McpCapability/McpConfigStrategy/McpTransport)
- M1 injection conf MCP au LaunchAgent + prose adaptée selon la surface
- M2 serveur/adapter MCP (JSON-RPC 2.0 maison ; outils idea_*) + ListAgents
- M3 câblage par projet (registre mcp_servers jumeau du watcher)
- M4 observabilité UI : OrchestratorRequestProcessed.source = file|mcp + badge

Trois portes d'entrée (fichier, MCP, UI) → un seul dispatch ; aucun nouveau
port applicatif ; MCP confiné à l'adapter infra. Tous lots verts (cycle §3).
Cadrage : .ideai/briefs/orchestration-v3-cadrage.md ; ARCHITECTURE.md §14.3.

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

frontend/src/features/agents/useAgents.ts

@@ -30,6 +30,13 @@ export interface AgentsViewModel {
   profiles: AgentProfile[];
   /** Agents that currently own a live PTY session, as tracked by IdeA. */
   liveAgents: LiveAgent[];
+  /**
+   * The entry door (`"mcp"` | `"file"`) the *last* orchestration delegation from
+   * each requester agent arrived through, keyed by requester id. Populated from
+   * `orchestratorRequestProcessed` events; a requester absent here (or an event
+   * without `source`) yields no badge.
+   */
+  delegationSourceByRequester: Record<string, "mcp" | "file">;
   /** Last error message, or `null`. */
   error: string | null;
   /** Whether a request is in flight. */
@@ -96,6 +103,9 @@ export function useAgents(projectId: string): AgentsViewModel {
   const [error, setError] = useState<string | null>(null);
   const [busy, setBusy] = useState(false);
   const [runningAgentId, setRunningAgentId] = useState<string | null>(null);
+  const [delegationSourceByRequester, setDelegationSourceByRequester] = useState<
+    Record<string, "mcp" | "file">
+  >({});
 
   const refresh = useCallback(async () => {
     setBusy(true);
@@ -150,6 +160,19 @@ export function useAgents(projectId: string): AgentsViewModel {
           void refresh();
           void refreshLiveAgents();
         }
+        // Record which door a delegation came through (mcp vs file). Absent
+        // `source` (older backend) leaves the map untouched → no badge.
+        if (
+          event.type === "orchestratorRequestProcessed" &&
+          event.source !== undefined
+        ) {
+          const { requesterId, source } = event;
+          setDelegationSourceByRequester((prev) =>
+            prev[requesterId] === source
+              ? prev
+              : { ...prev, [requesterId]: source },
+          );
+        }
       })
       .then((un) => {
         if (cancelled) un();
@@ -317,6 +340,7 @@ export function useAgents(projectId: string): AgentsViewModel {
     context,
     profiles,
     liveAgents,
+    delegationSourceByRequester,
     error,
     busy,
     runningAgentId,