fix(test): run the server suite on a private tmux server

Several suites start real `agenthub-lane-<id>` tmux sessions and then kill
or reset them, with lane ids from their own throwaway database. On the
user's default tmux server those names collide with the dashboard's real
lane panes, so a test run — including the one the pre-commit hook runs on
every commit — killed whichever live session shared an id, the pane the
commit was made from included.

`npm run test:server` now goes through scripts/test-server.js, which drops
TMUX, points TMUX_TMPDIR at a fresh directory and kills that server after.
Also fixes the ERUNTIMEOUT test's tmux mock, which had the wrong (async,
cmd+args) signature and only passed by accident.

scripts/test-server.js

@@ -0,0 +1,42 @@
+#!/usr/bin/env node
+/**
+ * @file test-server.js
+ * @description Runs the server test suite against a PRIVATE tmux server.
+ * Several suites start real `agenthub-lane-<id>` tmux sessions and then kill
+ * or reset them, with lane ids from their own throwaway database — on the
+ * user's default tmux server those names collide with the dashboard's real
+ * lane panes, and a test run kills whichever live session shares an id
+ * (including the pane the test was launched from). Dropping `TMUX` and
+ * pointing `TMUX_TMPDIR` at a fresh directory gives every tmux call — the
+ * app's own and the tests' direct `execFileSync("tmux", …)` — its own socket.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const { spawnSync } = require("node:child_process");
+const fs = require("node:fs");
+const os = require("node:os");
+const path = require("node:path");
+
+const root = path.join(__dirname, "..");
+const dir = path.join(root, "server", "__tests__");
+const files = fs
+  .readdirSync(dir)
+  .filter((f) => f.endsWith(".test.js"))
+  .map((f) => path.join(dir, f));
+const args = process.argv.slice(2);
+
+const tmuxDir = fs.mkdtempSync(path.join(os.tmpdir(), "agenthub-test-tmux-"));
+const env = { ...process.env, TMUX_TMPDIR: tmuxDir };
+delete env.TMUX;
+delete env.TMUX_PANE;
+
+const result = spawnSync(process.execPath, ["--test", ...args, ...(args.length ? [] : files)], {
+  stdio: "inherit",
+  env,
+  cwd: root,
+});
+
+// Whatever a test leaked dies with the private server, never a real pane.
+spawnSync("tmux", ["kill-server"], { env, stdio: "ignore" });
+fs.rmSync(tmuxDir, { recursive: true, force: true });
+process.exit(result.status ?? 1);