fix: v2.5.8 — the browser terminal attaches on Windows

node-pty on Windows looks the file it starts up on PATH exactly as given and
never adds `.exe`, so `tmux attach-session` started as a bare `tmux` failed
with "File not found" on every attach: the browser's terminal socket opened,
closed, and reconnected every 1.5 s.

- pty-attach.js: attachBinary names tmux by its full file name on Windows
  (ai-tools.which("tmux"), else tmux.exe)
- websocket.js: an attach that throws is logged as `[WS] attach <run> failed`,
  the one place that says why the terminal keeps reconnecting

server/__tests__/pty-attach.test.js

@@ -169,3 +169,17 @@ describe("pty-attach", () => {
     assert.equal(killed, true);
   });
 });
+
+describe("attachBinary on Windows", () => {
+  it("names tmux with its extension — node-pty there never adds `.exe`", () => {
+    // A bare `tmux` made node-pty answer "File not found" on every attach, so
+    // the browser's terminal opened, closed and reconnected every 1.5 s.
+    const saved = process.env.PATH;
+    process.env.PATH = "";
+    try {
+      assert.equal(ptyAttach.attachBinary("win32"), "tmux.exe");
+    } finally {
+      process.env.PATH = saved;
+    }
+  });
+});

server/lib/pty-attach.js

@@ -42,9 +42,14 @@ function __setSpawnImpl(fn) {
  * file), else `tmux` on PATH. A client must match its server — tmux installed
  * in a newer version while the server runs makes PATH's client fail every
  * attach with "open terminal failed: not a terminal", though every other tmux
- * command still works. Linux only; elsewhere PATH's tmux as before.
+ * command still works. Linux only; elsewhere PATH's tmux as before — on
+ * Windows by its full file name: node-pty there looks the file up on PATH as
+ * given, never adding `.exe`, so a bare `tmux` failed every attach with
+ * "File not found" (the browser saw a socket that opened and closed, again
+ * every 1.5 s).
  */
-function attachBinary() {
+function attachBinary(platform = process.platform) {
+  if (platform === "win32") return require("./ai-tools").which("tmux") || "tmux.exe";
   const pid = tmux.serverPid();
   if (!pid) return "tmux";
   const exe = `/proc/${pid}/exe`;
@@ -153,4 +158,4 @@ function attach(ws, runId, { cols, rows }) {
 // resolves a working native binding with no compiler needed.
 __setSpawnImpl((...args) => require("@lydell/node-pty").spawn(...args));
 
-module.exports = { attach, validateRunId, __setSpawnImpl };
+module.exports = { attach, attachBinary, validateRunId, __setSpawnImpl };

server/websocket.js

@@ -121,6 +121,9 @@ function initPtyWebSocket(server) {
     try {
       attach(ws, runId, size || { cols: 80, rows: 24 });
     } catch (err) {
+      // The browser only sees a socket that closed and retries every 1.5 s;
+      // this line is the one place that says why.
+      console.warn(`[WS] attach ${runId} failed:`, err.message);
       try {
         ws.close(1008, err.message);
       } catch {