fix(terminal): psmux wheel scrolling, per-platform tmux upgrade advice, Windows-safe server tests

- Server tests on Windows no longer reach the user's real psmux: psmux
  ignores TMUX_TMPDIR (and 3.3.x PSMUX_DATA_DIR), so quit.test.js's Quit and
  the runner's kill-server ended every live lane pane — the pre-commit hook
  included. scripts/test-server.js now takes tmux off the suites' PATH there.
- Wheel scrolling on Windows: psmux never turns mouse tracking on for its
  client, so xterm.js never reported the wheel and a pane could not scroll.
  A Windows attach is told {type:"wheel"} and the browser sends the SGR wheel
  report itself; psmux scrolls or forwards it to the pane's app.
- tmux.upgradeAdvice(): the oldest tmux AgentHub asks for and how each
  platform upgrades (psmux 3.4.0 -> winget upgrade marlocarlo.psmux; tmux 3.7
  -> brew upgrade tmux / build the release on Linux). Used by the doctor,
  GET /api/run/tmux ({available, version, upgrade}), `agenthub doctor`, and a
  sticky toast on the Workspace page. Advice only: nothing installs tmux.

Committed with --no-verify (user's call): the pre-commit hook runs the full
backend suite, which has ~378 pre-existing failures on Windows (S3/Linux-only
tests: sudo, /proc, systemd, members). Every test touching this change passes:
pty-attach, tmux, run, plugin-doctor-tmux, TerminalView, Workspace, and the
client tests related to the changed files; tsc and the header audit are clean.

client/src/components/run/TerminalView.tsx

@@ -355,9 +355,20 @@ export const TerminalView = memo(function TerminalView({
       // `false` also blocks tmux's own wheel scrolling. `x10` counts as off here
       // because that protocol reports button presses only, never the wheel — so
       // xterm takes the emulation path for it as well.
-      term.attachCustomWheelEventHandler(() => {
+      // psmux (Windows) never turns tracking on, so xterm never reports the
+      // wheel there; on the server's `{type:"wheel"}` this pane sends the SGR
+      // wheel report itself — psmux scrolls, or hands it to the pane's app.
+      // ponytail: at 1;1, which is all psmux reports to the app anyway.
+      let ownWheel = false;
+      term.attachCustomWheelEventHandler((ev) => {
         const mode = term.modes.mouseTrackingMode;
         const tracked = mode !== "none" && mode !== "x10";
+        if (!tracked && ownWheel) {
+          if (ev.deltaY && wsRef.current?.readyState === WebSocket.OPEN) {
+            wsRef.current.send(`\x1b[<${ev.deltaY < 0 ? 64 : 65};1;1M`);
+          }
+          return false;
+        }
         return tracked || term.buffer.active.type !== "alternate";
       });
 
@@ -530,6 +541,8 @@ export const TerminalView = memo(function TerminalView({
                   requestAnimationFrame(scaleToFit);
                 } else if (msg.type === "lead") {
                   takeLead();
+                } else if (msg.type === "wheel") {
+                  ownWheel = true;
                 } else if (msg.type === "exit") {
                   ended = true;
                   term.write(`\r\n${tRef.current("terminal.ended", { code: msg.code })}\r\n`);

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

@@ -231,6 +231,24 @@ describe("TerminalView", () => {
     expect(wheelHandlerMock.mock.calls[0]![0]!(new Event("wheel"))).toBe(false);
   });
 
+  it("sends the wheel itself once the server says its tmux never tracks the mouse", () => {
+    // psmux (Windows) never turns mouse tracking on for its client, so xterm
+    // never reports the wheel and the pane could not be scrolled at all.
+    termState.modes.mouseTrackingMode = "none";
+    termState.buffer.active.type = "alternate";
+    render(<TerminalView runId="agenthub-lane-1" wsBaseUrl="ws://localhost:4820" />);
+    const ws = MockWebSocket.instances[MockWebSocket.instances.length - 1]!;
+    ws.onmessage?.({ data: '{"type":"wheel"}' });
+    const wheel = wheelHandlerMock.mock.calls[wheelHandlerMock.mock.calls.length - 1]![0]!;
+    expect(wheel(new WheelEvent("wheel", { deltaY: -100 }))).toBe(false);
+    expect(wheel(new WheelEvent("wheel", { deltaY: 100 }))).toBe(false);
+    expect(ws.sent).toEqual(["\x1b[<64;1;1M", "\x1b[<65;1;1M"]);
+    // Tracked again (a tmux that does report): xterm sends it, never twice.
+    termState.modes.mouseTrackingMode = "any";
+    expect(wheel(new WheelEvent("wheel", { deltaY: -100 }))).toBe(true);
+    expect(ws.sent).toHaveLength(2);
+  });
+
   it("keeps Shift+Tab in the terminal instead of letting focus escape", () => {
     render(<TerminalView runId="agenthub-lane-1" wsBaseUrl="ws://localhost:4820" />);
     const handler = keyHandlerMock.mock.calls[0]![0]! as (e: KeyboardEvent) => boolean;

client/src/i18n/locales/en/lanes.json

@@ -617,5 +617,6 @@
   "fx.readOnlyHome": "Another user's home — view and download only",
   "fx.readOnly": "Read-only",
   "fx.readOnlyHint": "This is another user's home: you can view, copy and download, not change it.",
-  "fx.homeEmpty": "Nothing in your home yet — its hidden files (.bashrc, .claude…) are not shown here. Your workspaces are on the left."
+  "fx.homeEmpty": "Nothing in your home yet — its hidden files (.bashrc, .claude…) are not shown here. Your workspaces are on the left.",
+  "tmuxUpgrade": "Upgrade tmux: {{advice}}"
 }

client/src/i18n/locales/vi/lanes.json

@@ -617,5 +617,6 @@
   "fx.readOnlyHome": "Home của user khác — chỉ xem và tải về",
   "fx.readOnly": "Chỉ đọc",
   "fx.readOnlyHint": "Đây là home của user khác: bạn chỉ xem, sao chép và tải về được, không sửa được.",
-  "fx.homeEmpty": "Home của bạn chưa có thư mục nào — các file ẩn (.bashrc, .claude…) không hiện ở đây. Các workspace nằm ở danh sách bên trái."
+  "fx.homeEmpty": "Home của bạn chưa có thư mục nào — các file ẩn (.bashrc, .claude…) không hiện ở đây. Các workspace nằm ở danh sách bên trái.",
+  "tmuxUpgrade": "Cần nâng cấp tmux: {{advice}}"
 }

client/src/lib/api.ts

@@ -2936,8 +2936,12 @@ export const api = {
     /** GET /api/run/binary - whether the lane tool's CLI was found on PATH (fresh look). */
     binary: (tool: LaneTool = "claude") =>
       request<{ found: boolean; path: string | null }>(`/run/binary?tool=${tool}`),
-    /** GET /api/run/tmux - whether the `tmux` binary was found on PATH. */
-    tmuxAvailable: () => request<{ available: boolean }>("/run/tmux"),
+    /** GET /api/run/tmux - whether the `tmux` binary was found on PATH, its
+     *  version, and this platform's upgrade advice when it is too old. */
+    tmuxAvailable: () =>
+      request<{ available: boolean; version?: string | null; upgrade?: string | null }>(
+        "/run/tmux"
+      ),
     /** GET /api/run/cwds - suggested working directories for the cwd picker. */
     cwds: () => request<{ items: CwdSuggestion[] }>("/run/cwds"),
     /** GET /api/run/files - path-completion suggestions under `cwd`; `dirs`

client/src/pages/Workspace.tsx

@@ -665,6 +665,25 @@ export function Workspace() {
   const { local } = usePermissions();
   const [searchParams, setSearchParams] = useSearchParams();
 
+  // The server's tmux is older than this platform needs (psmux < 3.4.0 on
+  // Windows, tmux < 3.7 elsewhere): say how to upgrade it, until it is.
+  // Sticky (an error toast) so the command can be copied. An older server or
+  // no answer says nothing.
+  useEffect(() => {
+    let live = true;
+    (async () => {
+      try {
+        const { upgrade } = await api.run.tmuxAvailable();
+        if (live && upgrade) toast.error(tLanes("tmuxUpgrade", { advice: upgrade }));
+      } catch {
+        /* nothing to say */
+      }
+    })();
+    return () => {
+      live = false;
+    };
+  }, [tLanes]);
+
   // Lane state: the list is the shared store the sidebar reads too; the
   // selection is the URL's `?lane=` (the sidebar sets it, so does a
   // notification click), falling back to the last one shown, then the first.

client/src/pages/__tests__/Workspace.test.tsx

@@ -459,6 +459,23 @@ describe("Workspace page — lane integration", () => {
 });
 
 describe("Workspace layout", () => {
+  it("asks the user to upgrade a tmux older than their platform needs", async () => {
+    const { toast } = await import("../../lib/toast");
+    const shown = vi.spyOn(toast, "error");
+    const run = api.run as unknown as Record<string, unknown>;
+    run.tmuxAvailable = vi.fn().mockResolvedValue({
+      available: true,
+      version: "3.3.2",
+      upgrade: "psmux 3.3.2 is older than 3.4.0 — winget upgrade marlocarlo.psmux",
+    });
+    onTestFinished(() => {
+      delete run.tmuxAvailable;
+      shown.mockRestore();
+    });
+    await renderWorkspace();
+    expect(shown).toHaveBeenCalledWith(expect.stringContaining("winget upgrade marlocarlo.psmux"));
+  });
+
   it("shows no empty banner when there is no workspace (the sidebar's + adds one)", async () => {
     lanesToReturn = [];
     await renderWorkspace();