fix: v2.5.7 — panes work on psmux, the Windows tmux

psmux (the WinGet `tmux` on Windows) has no `=name` exact-match targets: it
answered "no server running on session '=agenthub-lane-1'" for a live pane,
so every Windows start reported "the session's command exited as soon as it
started" while the session ran on, and the browser could not attach.

- server/lib/tmux.js: `session`/`pane` targets probe the first live session
  once — `=name` failing where the bare name answers means bare names from
  then on; real tmux keeps `=name` / `=name:` (it matches by prefix otherwise)
- pty-attach.js and cc-update-all-helper.js use the same targets

server/lib/pty-attach.js

@@ -70,7 +70,7 @@ function attach(ws, runId, { cols, rows }) {
   } catch {
     /* session gone or tmux unavailable — attach below will surface that */
   }
-  const pty = spawnImpl(attachBinary(), ["attach-session", "-t", `=${runId}`], {
+  const pty = spawnImpl(attachBinary(), ["attach-session", "-t", tmux.session(runId)], {
     name: "xterm-256color",
     cols: cols || 80,
     rows: rows || 24,

server/lib/tmux.js

@@ -26,19 +26,58 @@ const { execFileSync } = require("node:child_process");
 const EXEC_OPTS = { encoding: "utf8", stdio: ["pipe", "pipe", "ignore"] };
 let execImpl = (args) => execFileSync("tmux", args, EXEC_OPTS);
 
-function __setExecImpl(fn) {
+// Whether this tmux takes `=name` targets: true for tmux itself, false for
+// psmux (the WinGet `tmux` on Windows), null until a live session has shown
+// which. A fake exec in a test is real tmux unless it says otherwise.
+let exactTargets = null;
+
+function __setExecImpl(fn, { exact = true } = {}) {
   execImpl = fn;
+  exactTargets = exact;
 }
 function __reset() {
   execImpl = (args) => execFileSync("tmux", args, EXEC_OPTS);
+  exactTargets = null;
+}
+
+/**
+ * Probe once, on a session that exists: `=name` failing where the bare name
+ * answers means this tmux has no exact-match syntax (psmux answers
+ * "no server running on session '=name'"), so every target there is the bare
+ * name. Until a session exists to ask, tmux's own syntax.
+ */
+function exact() {
+  if (exactTargets !== null) return exactTargets;
+  let first;
+  try {
+    first = String(execImpl(["list-sessions", "-F", "#{session_name}"]))
+      .split("\n")
+      .map((x) => x.trim())
+      .find(Boolean);
+  } catch {
+    return true;
+  }
+  if (!first) return true;
+  const answers = (t) => {
+    try {
+      execImpl(["has-session", "-t", t]);
+      return true;
+    } catch {
+      return false;
+    }
+  };
+  if (answers(`=${first}`)) exactTargets = true;
+  else if (answers(first)) exactTargets = false;
+  return exactTargets ?? true;
 }
 
 // tmux resolves a bare `-t agenthub-lane-1` by PREFIX when no exact match
 // exists, so it would hit `agenthub-lane-12` once lane 1's session is gone —
 // and killSession would kill the wrong lane. `=` forces an exact match; pane
 // and option targets need the trailing `:` (tmux 3.4 rejects `=name` there).
-const session = (name) => `=${name}`;
-const pane = (name) => `=${name}:`;
+// psmux has neither form and names a session by its bare name.
+const session = (name) => (exact() ? `=${name}` : name);
+const pane = (name) => (exact() ? `=${name}:` : name);
 
 function hasSession(name) {
   try {
@@ -247,6 +286,8 @@ function serverVersion() {
 }
 
 module.exports = {
+  session,
+  pane,
   hasSession,
   newSession,
   enableMouse,