feat(agent): vue chat frontend + routage cellKind (D5) — §17

Le frontend consomme l'exécution structurée livrée en D4 :
- AgentChatView : jumeau chat de TerminalView. Accumule les textDelta du
  tour courant, badges toolActivity, fige sur final (le contenu final
  remplace les deltas, pas de double rendu). Saisie Enter/Shift+Enter.
  Au montage : reattach (rejoue le scrollback) ou launch ; au démontage :
  détache seulement (jamais de close). Vue pure pilotée par le port.
- LayoutGrid/LeafView : routage cellKind — AgentChatView si "chat",
  TerminalView sinon (chemin PTY inchangé). Cache cellKindBySession pour
  router correctement après ré-attache/navigation.
- Port AgentGateway : sendPrompt / reattachChat / closeAgentSession ;
  cellKind sur TerminalHandle. Adapter Tauri (invoke + Channel<ReplyChunk>)
  et mock (MockChatSession, _setChatAgents) étendus.
- Types TS mirrors : CellKind, ReplyChunk, ReattachChatDto + cellKind sur
  TerminalSession.

Tests (QA) : 21 Vitest verts — routage chat/pty (non-régression terminal),
accumulation/non-doublon (garde anti-always-green delta!=final), ré-attache
sans re-spawn, envoi Enter vs Shift+Enter, badges toolActivity, mock stream.
npx vitest run : 345 passed, 0 failed. npm run build vert.

Reste D6 (messagerie inter-agents via send_blocking) et D7 (menu restreint
Claude/Codex + retrait custom) pour clore §17.

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

frontend/src/adapters/agent.ts

@@ -14,7 +14,14 @@
 
 import { Channel, invoke } from "@tauri-apps/api/core";
 
-import type { Agent, ResumableAgent, TerminalSession } from "@/domain";
+import type {
+  Agent,
+  CellKind,
+  ReattachChatDto,
+  ReplyChunk,
+  ResumableAgent,
+  TerminalSession,
+} from "@/domain";
 import type {
   AgentGateway,
   ConversationDetails,
@@ -34,6 +41,8 @@ interface LaunchAgentResponse {
   cols: number;
   /** Conversation id minted by this launch (omitted when nothing was assigned). */
   assignedConversationId?: string;
+  /** How the hosting cell should render (`"chat"` ⇒ structured AI cell, §17.6). */
+  cellKind: CellKind;
 }
 
 export class TauriAgentGateway implements AgentGateway {
@@ -144,12 +153,17 @@ export class TauriAgentGateway implements AgentGateway {
       onOutput: channel,
     });
 
-    const handle = makeTerminalHandle(res.sessionId, channel);
-    // Surface the id assigned by this launch so the caller persists it on the
-    // leaf (`setCellConversation`) and resumes next time.
-    return res.assignedConversationId
-      ? { ...handle, assignedConversationId: res.assignedConversationId }
-      : handle;
+    const base = makeTerminalHandle(res.sessionId, channel);
+    // Surface the id assigned by this launch (so the caller persists it on the
+    // leaf and resumes next time) and the derived `cellKind` (so the leaf routes
+    // to `AgentChatView` vs `TerminalView`, §17.6).
+    return {
+      ...base,
+      cellKind: res.cellKind,
+      ...(res.assignedConversationId
+        ? { assignedConversationId: res.assignedConversationId }
+        : {}),
+    };
   }
 
   async reattach(
@@ -183,4 +197,40 @@ export class TauriAgentGateway implements AgentGateway {
       request: { projectId, agentId, conversationId },
     });
   }
+
+  async sendPrompt(
+    sessionId: string,
+    prompt: string,
+    onReply: (chunk: ReplyChunk) => void,
+  ): Promise<void> {
+    // Per-turn reply channel. The backend streams typed `ReplyChunk`s (tagged on
+    // `kind`); the pump runs to the `final` chunk then detaches its generation.
+    const channel = new Channel<ReplyChunk>();
+    channel.onmessage = (chunk) => onReply(chunk);
+
+    // `agent_send` takes top-level args (Tauri renames the snake_case command
+    // params to camelCase): `sessionId`, `prompt`, `onReply`.
+    await invoke("agent_send", { sessionId, prompt, onReply: channel });
+  }
+
+  async reattachChat(
+    sessionId: string,
+    onReply: (chunk: ReplyChunk) => void,
+  ): Promise<ReplyChunk[]> {
+    // Re-bind to a still-living structured session without re-spawning it. The
+    // returned scrollback repaints prior turns; subsequent chunks arrive over the
+    // freshly-registered channel.
+    const channel = new Channel<ReplyChunk>();
+    channel.onmessage = (chunk) => onReply(chunk);
+
+    const res = await invoke<ReattachChatDto>("reattach_agent_chat", {
+      sessionId,
+      onReply: channel,
+    });
+    return res.scrollback;
+  }
+
+  async closeAgentSession(sessionId: string): Promise<void> {
+    await invoke("close_agent_session", { sessionId });
+  }
 }