fix(chat): réattache persistante CLI custom et rendu tools/MCP/progress enrichi (#188)

Corrige la perte de session à la navigation: le démontage du CustomAgentChatView
appelait close_agent_session (destructeur) au lieu de simplement détacher le
transport. Désormais:

- nouvelle commande Tauri detach_agent_chat (+ ChatBridge::detach) qui libère le
  canal sans tuer la session ni le scrollback retenu; distinct de
  close_agent_session qui reste le close destructeur explicite;
- le frontend appelle detachAgentChat à l'unmount puis restore sa vue depuis un
  cache de session (turns + chunkCount) à la réattache;
- message « Reprise effectuée: N événements rattrapés… » quand la réattache
  rejoue plus de chunks que le cache local n'en avait conservé.

Enrichit le rendu tools/MCP/progress:

- ProgressSettler (chat bridge) émet un progress completed synthétique quand un
  spinner reste ouvert (nouvelle entité progress, chunk text/final/error): fini
  les spinners fantômes;
- les adapters claude/codex/opencode/openai_compat extraient un aperçu du
  payload (arguments/input/command/message/params) attaché au progress;
- bounded_reply_progress_preview (domain) garde les 4 premières lignes non
  vides, normalisation CR/LF;
- previewText (frontend) multiligne whitespace-pre-wrap, source/nativeEvent
  affichés sous le titre; suppression du flag settled et du Spinner inline
  devenus redondants (l'état est porté par le stage + le settler).

Tests: detach_agent_chat gateway (Tauri + mock), ProgressSettler, bornage
reply_progress, item_preview/tool_preview par adapter, réattache avec cache et
notice de rattrapage.

frontend/src/features/agents/CustomAgentChatView.test.tsx

@@ -1,9 +1,9 @@
 import { act, fireEvent, render, screen, waitFor } from "@testing-library/react";
 import { useState } from "react";
-import { describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import { DIProvider } from "@/app/di";
-import type { AgentProfile } from "@/domain";
+import type { AgentProfile, ReplyChunk } from "@/domain";
 import { PluginRuntimeProvider } from "@/features/plugins";
 import {
   PluginCommandRegistry,
@@ -12,7 +12,10 @@ import {
   PluginRuntimeRegistry,
 } from "@/plugins/runtime";
 import type { ChatDraftScope, Gateways } from "@/ports";
-import { CustomAgentChatView } from "./CustomAgentChatView";
+import {
+  CustomAgentChatView,
+  __clearCustomAgentChatViewCacheForTests,
+} from "./CustomAgentChatView";
 
 const profile: AgentProfile = {
   id: "structured",
@@ -57,6 +60,11 @@ function addPluginCommand(
 }
 
 describe("CustomAgentChatView", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    __clearCustomAgentChatViewCacheForTests();
+  });
+
   it("repaints attachment labels from user prompt scrollback", async () => {
     const agent = {
       launchAgentChat: vi.fn(),
@@ -101,6 +109,75 @@ describe("CustomAgentChatView", () => {
     expect(screen.getByText("Fichier: clipboard.png")).toBeTruthy();
   });
 
+  it("detaches on unmount then reattaches with missed scrollback chunks", async () => {
+    let scrollback: ReplyChunk[] = [
+      { kind: "userPrompt" as const, text: "Initial prompt" },
+      { kind: "textDelta" as const, text: "Initial reply" },
+    ];
+    const agent = {
+      launchAgentChat: vi.fn(),
+      reattachAgentChat: vi.fn(async (sessionId: string) => ({
+        sessionId,
+        scrollback,
+      })),
+      detachAgentChat: vi.fn(async () => {}),
+      sendAgentChat: vi.fn(async () => {}),
+      cancelAgentChat: vi.fn(async () => {}),
+      closeAgentChat: vi.fn(async () => {}),
+    };
+    const props = {
+      projectId: "project-1",
+      agentId: "agent-1",
+      agentName: "Worker",
+      profile,
+      cwd: "/repo",
+      nodeId: "node-1",
+      sessionId: "chat-session-1",
+      conversationId: "conversation-1",
+      onSessionId: vi.fn(),
+      onConversationId: vi.fn(),
+    };
+
+    const first = render(
+      <DIProvider
+        gateways={{
+          agent,
+          system: { pickFile: vi.fn(async () => null) },
+        } as unknown as Gateways}
+      >
+        <CustomAgentChatView {...props} />
+      </DIProvider>,
+    );
+
+    expect(await screen.findByText("Initial reply")).toBeTruthy();
+    first.unmount();
+    await waitFor(() => expect(agent.detachAgentChat).toHaveBeenCalledWith("chat-session-1"));
+
+    scrollback = [
+      ...scrollback,
+      { kind: "toolActivity" as const, label: "Background tool" },
+      { kind: "final" as const, content: "Completed away" },
+    ];
+
+    render(
+      <DIProvider
+        gateways={{
+          agent,
+          system: { pickFile: vi.fn(async () => null) },
+        } as unknown as Gateways}
+      >
+        <CustomAgentChatView {...props} />
+      </DIProvider>,
+    );
+
+    expect(screen.getByText("Initial reply")).toBeTruthy();
+    expect(await screen.findByText("Background tool")).toBeTruthy();
+    expect(screen.getByText("Completed away")).toBeTruthy();
+    expect(
+      screen.getByText("Reprise effectuée: 2 événements rattrapés pendant l'absence."),
+    ).toBeTruthy();
+  });
+
   it("stops the live agent with cascade feedback and releases the structured session", async () => {
     let resolveStop: (value: {
       agentId: string;
@@ -614,7 +691,7 @@ describe("CustomAgentChatView", () => {
 
     expect(screen.getByText("Worker → QA")).toBeTruthy();
     expect(screen.getByText("Worker → QA").parentElement?.textContent).toContain("started");
-    expect(screen.getAllByRole("status", { name: "Loading" }).length).toBeGreaterThan(0);
+    expect(screen.queryByRole("status", { name: "Loading" })).toBeNull();
 
     act(() => {
       emitChunk?.(progress("providerNative", "completed"));
@@ -638,7 +715,7 @@ describe("CustomAgentChatView", () => {
     );
   });
 
-  it("stops animating running progress rows once the turn reaches a final chunk", async () => {
+  it("renders running progress without spinner and marks it done on final", async () => {
     let emitChunk: ((chunk: unknown) => void) | null = null;
     const agent = {
       launchAgentChat: vi.fn(),
@@ -707,7 +784,7 @@ describe("CustomAgentChatView", () => {
       });
     });
 
-    expect(screen.getAllByRole("status", { name: "Loading" }).length).toBeGreaterThan(0);
+    expect(screen.queryByRole("status", { name: "Loading" })).toBeNull();
     expect(screen.getByText("Progress").parentElement?.textContent).toContain("running");
 
     act(() => {