feat: v2.6.0 — Chat UI composer (+ menu, project files, activity panel, permission mode, Stop), git on a workspace's extra folders (#70), long paste as a file (#68), S3 server mode (experimental)

Chat UI:
- Each Claude/Codex session keeps its own chat/terminal view; Settings only
  sets how new sessions open.
- Composer + menu: upload, project files and folders (#54, also dragged from
  the Files/Changes tree), context files, recent uploads, skills, plugins.
- Activity side panel (progress, outputs, files read, uploads, memory,
  skills, connectors) with a file preview; edited-file counts per turn.
- Permission-mode chip (Shift+Tab steps, read back from the pane:
  server/lib/pane-mode.js, GET|POST /api/run/:id/permission-mode).
- Stop (Esc) while the main agent works; the status is checked per agent
  (with session_id /api/agents ignores its status filter) and re-read every
  5 s while Stop shows.
- Dropped images shown in the conversation (GET /api/run/drop/:name, the
  requester's own drop dir), full-size viewer.
- A plain-text paste over 5,000 characters is attached as pasted-text.txt,
  so no prompt reaches tmux/argv limits (#68).

Changes panel: every /api/lanes/:id/git* route takes ?source=<lane_sources
id> (sourceFolder; ENOSOURCE otherwise) and a folder picker switches the
whole panel to a workspace's extra folder (#70).

Server mode S3 (one Linux user per account) — experimental, verified with
fake sudo plus a P6 managed-settings spike on a test account:
- member tmux listing runs in the background (cached, 15 s => unknown);
- transcript snapshot copy is async, chunked, temp file + rename;
- Express Layer patch only on Express 4;
- tmux capturePane/sendKey go to the member's own server.

Docs: the multi-user design moved in as docs/plans/server-mode/README.md
(the AgentHub-Server repo is gone); S3-PLAN P6 result; LANES/API/openapi.

client/src/components/run/__tests__/LaneConsolePane.test.tsx

@@ -7,13 +7,13 @@
  */
 
 import { describe, it, expect, vi, beforeEach } from "vitest";
-import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import { act, render, screen, fireEvent, waitFor } from "@testing-library/react";
 import { MemoryRouter } from "react-router-dom";
 import { LaneConsolePane } from "../LaneConsolePane";
 import { api } from "../../../lib/api";
 import type { Lane } from "../../../lib/types";
 import { __resetAiTools } from "../../../hooks/useAiTools";
-import { __resetChatUi } from "../../../lib/chatUi";
+import { VIEWS_KEY, __resetChatUi, saveChatUi, setSessionChat } from "../../../lib/chatUi";
 
 vi.mock("../TerminalView", () => ({
   // The exit button stands in for the server's `exit` frame (a double Ctrl+C
@@ -33,7 +33,10 @@ vi.mock("../PaneChat", () => ({
 
 vi.mock("../../../lib/api", () => ({
   api: {
-    me: { prefs: vi.fn().mockResolvedValue({ prefs: {}, onboardedAt: null }) },
+    me: {
+      prefs: vi.fn().mockResolvedValue({ prefs: {}, onboardedAt: null }),
+      savePrefs: vi.fn(),
+    },
     lanes: {
       ensure: vi.fn(),
       action: vi.fn(),
@@ -171,7 +174,41 @@ describe("LaneConsolePane", () => {
     render(<LaneConsolePane {...baseProps()} activeRuns={{ items: [live] }} />);
     expect(await screen.findByTestId("pane-chat")).toHaveAttribute("data-session-id", "s-1");
     expect(screen.getByTestId("terminal-view")).toBeInTheDocument();
-    expect(screen.queryByTestId("pane-view-chat")).toBeNull(); // no per-pane switch
+    __resetChatUi();
+  });
+
+  it("keeps each session's own view: the Chat UI setting is only a new session's default", async () => {
+    vi.mocked(api.me.prefs).mockResolvedValueOnce({
+      prefs: { "agenthub.chatUi": "1" },
+      onboardedAt: null,
+    });
+    __resetChatUi();
+    const live = {
+      id: "agenthub-lane-1",
+      laneId: 1,
+      status: "running" as const,
+      cwd: "/workspace/a",
+      model: null,
+      permissionMode: null,
+      effort: null,
+      resumeSessionId: null,
+      sessionId: "s-1",
+      startedAt: null,
+      promptPreview: null,
+      tool: "claude" as const,
+    };
+    render(<LaneConsolePane {...baseProps()} activeRuns={{ items: [live] }} />);
+    expect(await screen.findByTestId("pane-chat")).toBeInTheDocument();
+    // Seen once, the session keeps chat: turning the default off leaves it alone.
+    await waitFor(() =>
+      expect(JSON.parse(localStorage.getItem(VIEWS_KEY) || "{}")).toEqual({ "s-1": true })
+    );
+    vi.mocked(api.me.savePrefs).mockResolvedValueOnce({ prefs: {}, onboardedAt: null });
+    await act(() => saveChatUi(false));
+    expect(screen.getByTestId("pane-chat")).toBeInTheDocument();
+    // Its own toggle switches it.
+    act(() => setSessionChat("s-1", false));
+    expect(screen.queryByTestId("pane-chat")).toBeNull();
     __resetChatUi();
   });