feat(chat): livre la CLI custom de chat agent (#147) et corrige Cancel

Implémente la vue chat structurée par cellule agent (toggle TUI/CLI custom,
préférence persistée `preferred_view`, reattach live, composer + pièces
jointes) avec le socle backend AgentSession/ChatBridge (UserPrompt,
cancel_current_turn, routage interrupt_agent, commande cancel_agent_chat).

Corrige le bug bloquant relevé par QA : le bouton Cancel de
CustomAgentChatView interrompait tout le tour via closeAgentChat au lieu
de n'annuler que le tour courant via cancelAgentChat, ce qui tuait la
session contrairement au contrat produit validé.

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

frontend/src/adapters/mock/index.ts

@@ -99,6 +99,7 @@ import type {
   Unsubscribe,
 } from "@/domain";
 import type {
+  AgentChatHandle,
   AgentGateway,
   ConversationGateway,
   ConversationPageRequest,
@@ -145,6 +146,7 @@ import type {
   PluginWorkspaceWriteBinaryInput,
   PluginWorkspaceWriteTextInput,
   ReattachResult,
+  ReattachAgentChatResult,
   RemoteGateway,
   ReviewPluginPackageInput,
   SaveOpenCodeProviderProfileInput,
@@ -392,6 +394,10 @@ export class MockAgentGateway implements AgentGateway {
   private liveByAgent = new Map<string, string>();
   /** Live PTY session id per agent (`agentId → sessionId`). */
   private liveSessionByAgent = new Map<string, string>();
+  /** Runtime kind per live agent (`agentId → kind`). */
+  private liveKindByAgent = new Map<string, "pty" | "structured">();
+  /** Retained structured reply chunks per live chat session. */
+  private chatScrollback = new Map<string, ReplyChunk[]>();
 
   private getAgents(projectId: string): Agent[] {
     if (!this.agents.has(projectId)) this.agents.set(projectId, []);
@@ -416,7 +422,7 @@ export class MockAgentGateway implements AgentGateway {
         agentId,
         nodeId,
         sessionId: this.liveSessionByAgent.get(agentId)!,
-        kind: "pty" as const,
+        kind: this.liveKindByAgent.get(agentId) ?? "pty",
       }));
   }
 
@@ -449,7 +455,11 @@ export class MockAgentGateway implements AgentGateway {
       throw err;
     }
     const sessionId = this.liveSessionByAgent.get(agentId);
-    if (!sessionId || !this.sessions.has(sessionId)) {
+    if (
+      !sessionId ||
+      (this.liveKindByAgent.get(agentId) !== "structured" &&
+        !this.sessions.has(sessionId))
+    ) {
       const err: GatewayError = {
         code: "NOT_FOUND",
         message: `agent ${agentId} has no live session`,
@@ -457,7 +467,12 @@ export class MockAgentGateway implements AgentGateway {
       throw err;
     }
     this.liveByAgent.set(agentId, nodeId);
-    return { agentId, nodeId, sessionId, kind: "pty" };
+    return {
+      agentId,
+      nodeId,
+      sessionId,
+      kind: this.liveKindByAgent.get(agentId) ?? "pty",
+    };
   }
 
   async stopLiveAgent(projectId: string, agentId: string): Promise<StoppedLiveAgent> {
@@ -480,9 +495,12 @@ export class MockAgentGateway implements AgentGateway {
     const session = this.sessions.get(sessionId);
     if (session) session.closed = true;
     this.sessions.delete(sessionId);
+    this.chatScrollback.delete(sessionId);
     this.liveSessionByAgent.delete(agentId);
     this.liveByAgent.delete(agentId);
-    return { agentId, sessionId, kind: "pty" };
+    const kind = this.liveKindByAgent.get(agentId) ?? "pty";
+    this.liveKindByAgent.delete(agentId);
+    return { agentId, sessionId, kind };
   }
 
   async createAgent(projectId: string, input: CreateAgentInput): Promise<Agent> {
@@ -718,11 +736,13 @@ export class MockAgentGateway implements AgentGateway {
     if (options.nodeId) {
       this.liveByAgent.set(agentId, options.nodeId);
       this.liveSessionByAgent.set(agentId, sessionId);
+      this.liveKindByAgent.set(agentId, "pty");
     }
     const clearLive = () => {
       if (this.liveByAgent.get(agentId) === options.nodeId) {
         this.liveByAgent.delete(agentId);
         this.liveSessionByAgent.delete(agentId);
+        this.liveKindByAgent.delete(agentId);
       }
     };
 
@@ -752,6 +772,101 @@ export class MockAgentGateway implements AgentGateway {
     return handle;
   }
 
+  async launchAgentChat(
+    projectId: string,
+    agentId: string,
+    options: OpenTerminalOptions,
+  ): Promise<AgentChatHandle> {
+    const list = this.getAgents(projectId);
+    if (!list.some((a) => a.id === agentId)) {
+      throw {
+        code: "NOT_FOUND",
+        message: `agent ${agentId} not found in project ${projectId}`,
+      } as GatewayError;
+    }
+    const liveNode = this.liveByAgent.get(agentId);
+    if (liveNode !== undefined && options.nodeId && liveNode !== options.nodeId) {
+      throw {
+        code: "AGENT_ALREADY_RUNNING",
+        message: `agent ${agentId} is already running in cell ${liveNode}`,
+      } as GatewayError;
+    }
+    this.sessionSeq += 1;
+    const sessionId = `mock-agent-chat-${this.sessionSeq}`;
+    this.chatScrollback.set(sessionId, []);
+    if (options.nodeId) {
+      this.liveByAgent.set(agentId, options.nodeId);
+      this.liveSessionByAgent.set(agentId, sessionId);
+      this.liveKindByAgent.set(agentId, "structured");
+    }
+    return {
+      sessionId,
+      ...(!options.conversationId
+        ? { assignedConversationId: `mock-conversation-${sessionId}` }
+        : {}),
+    };
+  }
+
+  async reattachAgentChat(
+    sessionId: string,
+    _onChunk: (chunk: ReplyChunk) => void,
+  ): Promise<ReattachAgentChatResult> {
+    const chunks = this.chatScrollback.get(sessionId);
+    if (!chunks) {
+      throw {
+        code: "NOT_FOUND",
+        message: `agent chat session ${sessionId} is not alive`,
+      } as GatewayError;
+    }
+    return { sessionId, scrollback: structuredClone(chunks) };
+  }
+
+  async sendAgentChat(
+    sessionId: string,
+    prompt: string,
+    onChunk: (chunk: ReplyChunk) => void,
+  ): Promise<void> {
+    const chunks = this.chatScrollback.get(sessionId);
+    if (!chunks) {
+      throw {
+        code: "NOT_FOUND",
+        message: `agent chat session ${sessionId} not found`,
+      } as GatewayError;
+    }
+    const content = `Agent: reçu « ${prompt} ».`;
+    const streamed: ReplyChunk[] = [
+      { kind: "toolActivity", label: "Analyse du prompt" },
+      { kind: "textDelta", text: "Agent: reçu " },
+      { kind: "textDelta", text: `« ${prompt} ».` },
+      { kind: "final", content },
+    ];
+    for (const chunk of streamed) {
+      await Promise.resolve();
+      chunks.push(structuredClone(chunk));
+      onChunk(chunk);
+    }
+  }
+
+  async closeAgentChat(sessionId: string): Promise<void> {
+    this.chatScrollback.delete(sessionId);
+    for (const [agentId, liveSessionId] of this.liveSessionByAgent) {
+      if (liveSessionId === sessionId) {
+        this.liveSessionByAgent.delete(agentId);
+        this.liveByAgent.delete(agentId);
+        this.liveKindByAgent.delete(agentId);
+      }
+    }
+  }
+
+  async cancelAgentChat(sessionId: string): Promise<void> {
+    if (!this.chatScrollback.has(sessionId)) {
+      throw {
+        code: "NOT_FOUND",
+        message: `agent chat session ${sessionId} not found`,
+      } as GatewayError;
+    }
+  }
+
   async reattach(
     sessionId: string,
     onData: (bytes: Uint8Array) => void,
@@ -772,6 +887,7 @@ export class MockAgentGateway implements AgentGateway {
           if (liveSessionId === sessionId) {
             this.liveSessionByAgent.delete(agentId);
             this.liveByAgent.delete(agentId);
+            this.liveKindByAgent.delete(agentId);
           }
         }
       }),