feat(workstate): UI des actions contrôlées (Lot D frontend)

Câble les actions contrôlées dans ProjectWorkStatePanel : port et adaptateur
agent étendus aux nouvelles commandes, adaptateur mock aligné.

Tests verts : workstate + projects (25), agent (8), singletonAgent +
agentAlreadyRunning (9), tsc --noEmit OK.

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

frontend/src/adapters/agent.ts

@@ -26,6 +26,7 @@ import type {
   LiveAgent,
   OpenTerminalOptions,
   ReattachResult,
+  StoppedLiveAgent,
   TerminalHandle,
 } from "@/ports";
 import { makeTerminalHandle } from "./terminal";
@@ -63,14 +64,14 @@ export class TauriAgentGateway implements AgentGateway {
     agentId: string,
     nodeId: string,
   ): Promise<LiveAgent> {
-    return invoke<LiveAgent[]>("attach_live_agent", {
+    return invoke<LiveAgent>("attach_live_agent", {
       request: { projectId, agentId, nodeId },
-    }).then((list) => {
-      const attached = list[0];
-      if (!attached) {
-        throw new Error(`running session for agent ${agentId} was not returned`);
-      }
-      return attached;
+    });
+  }
+
+  stopLiveAgent(projectId: string, agentId: string): Promise<StoppedLiveAgent> {
+    return invoke<StoppedLiveAgent>("stop_live_agent", {
+      request: { projectId, agentId },
     });
   }