fix: v2.5.6 — Windows panes without sh, UI build without node on PATH

- Windows panes: a WinGet tmux runs native programs and there is no `sh`, so
  every pane's `sh -c` wrapper died at once ("Command failed: tmux set-option
  … mouse on"). paneArgv runs the CLI itself on win32, and a Terminal gets
  tmux's own default shell (newSession drops the `--` for an empty argv).
- Plugin UI build: client deps install with --ignore-scripts and tsc/vite run
  by the running node instead of `npm run build`. On Windows esbuild's
  postinstall went through cmd.exe with no `node` on the server's PATH, both
  installs failed, and Update now kept the previous UI. A test keeps the two
  build steps equal to client/package.json's build script.
- Update all: Atomics.wait instead of a `sleep` binary Windows lacks.

server/__tests__/plugin-bootstrap.test.js

@@ -455,14 +455,18 @@ describe("buildClient dependency install", () => {
     return root;
   }
 
-  // Records every npm invocation; `fails` names the subcommands that exit non-zero.
-  // A successful "run build" writes the dist/ the real Vite build would produce.
+  // Records every invocation — npm's as its args, node's as `node <script> …`;
+  // `fails` names the npm subcommands that exit non-zero. A successful vite
+  // build writes the dist/ the real one would produce.
   function fakeExec(calls, fails = []) {
-    return (_cmd, args, cwd) => {
+    return (cmd, args, cwd) => {
+      if (cmd === "node") {
+        calls.push(`node ${path.basename(args[0])} ${args.slice(1).join(" ")}`);
+        if (args[1] === "build") fs.mkdirSync(path.join(cwd, "dist"), { recursive: true });
+        return true;
+      }
       calls.push(args.join(" "));
-      if (fails.includes(args[0])) return false;
-      if (args[0] === "run") fs.mkdirSync(path.join(cwd, "dist"), { recursive: true });
-      return true;
+      return !fails.includes(args[0]);
     };
   }
 
@@ -489,10 +493,12 @@ describe("buildClient dependency install", () => {
     const result = buildClient({ rt: RT, root: fakeRoot(), exec: fakeExec(calls, ["ci"]) });
 
     assert.equal(result, "built");
-    assert.deepEqual(
-      calls.map((c) => c.split(" ")[0]),
-      ["ci", "install", "run"]
-    );
+    assert.deepEqual(calls, [
+      "ci --no-audit --no-fund --include=dev --ignore-scripts",
+      "install --no-audit --no-fund --include=dev --ignore-scripts",
+      "node tsc -b",
+      "node vite.js build",
+    ]);
   });
 
   it("installs devDependencies explicitly, because NODE_ENV=production omits them", () => {
@@ -521,11 +527,28 @@ describe("buildClient dependency install", () => {
 
     assert.equal(result, "failed");
     assert.equal(
-      calls.some((c) => c.startsWith("run")),
+      calls.some((c) => c.startsWith("node")),
       false,
       "the build must not run on a broken dependency tree"
     );
   });
+
+  it("builds with the running node, no lifecycle script and no PATH lookup (Windows)", () => {
+    // On Windows a script or a .bin shim runs through cmd.exe and needs `node`
+    // on PATH; the server's PATH lacked it, so esbuild's postinstall failed and
+    // every update kept the previous UI. The build here must equal the
+    // client's own "build" script, run without npm.
+    assert.equal(
+      JSON.parse(fs.readFileSync(path.join(__dirname, "..", "..", "client", "package.json")))
+        .scripts.build,
+      "tsc -b && vite build"
+    );
+    resetRuntime();
+    const calls = [];
+    buildClient({ rt: RT, root: fakeRoot(), exec: fakeExec(calls) });
+    assert.deepEqual(calls.slice(-2), ["node tsc -b", "node vite.js build"]);
+    assert.ok(calls.every((c) => !c.startsWith("run")));
+  });
 });
 
 describe("supersededBy — an old cache directory must not act", () => {