feat: Windows daemon lifecycle (W3) — Startup-folder autostart

The Linux node runs under `systemctl --user`. Windows has no per-user
equivalent that works without elevation: `schtasks /create /sc ONLOGON`
(even `/rl LIMITED /it`) fails with "Access is denied" for a non-admin
user, because a logon trigger touches machine-wide scheduler state.

So autostart is a `.vbs` in the per-user Startup folder instead:

    CreateObject("WScript.Shell").Run Chr(34) & "<exe>" & Chr(34), 0, False

wscript runs it at every sign-in, hidden (0) and non-blocking. No admin,
no console window, no new dependency. Verified end to end: the launcher
brings the daemon up with no window and it answers its loopback API.

node/platform.py
  autostart_install/remove/status  — write / delete / detect the launcher
  autostart_run/end                — start now (DETACHED|NO_WINDOW) / taskkill
  _node_exe                        — PATH, then next to sys.executable, then argv[0]

node/daemon.py
  new `autostart install|remove|start|stop|status` verb
  reload (win32)         -> POST /api/reload on the loopback API
  restart-daemon (win32) -> autostart_end + autostart_run
  reset (win32)          -> also removes the launcher

client/main.js, preload.js
  node:autostart handler + winAutostart* helpers (kept in step with platform.py)
  node:service-status (win32) probes the daemon; stop/restart/start use
  taskkill + a detached, windowless spawn

Tests: 8 autostart cases in test_platform.py (mocked sys.platform, APPDATA
pointed at tmp); `autostart status` added to the CLI dispatch sweep. Full
meshbay-node suite green on Windows (784 passed / 34 skipped).

Still open: no CTRL_CLOSE_EVENT handler, so a bare taskkill / window close
does not run _shutdown() (SetConsoleCtrlHandler, follow-up). Service mode
(pywin32/NSSM) stays Phase 2.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

2 files changed, 80 insertions, 2 deletions

diff --git a/packages/meshbay-node/tests/test_cli_dispatch.py b/packages/meshbay-node/tests/test_cli_dispatch.py
index 76eb6d5..606e586 100644
--- a/packages/meshbay-node/tests/test_cli_dispatch.py
+++ b/packages/meshbay-node/tests/test_cli_dispatch.py
@@ -42,6 +42,7 @@ VERBS = [
     ["stun", "list"],
     ["reload"],
     ["restart-daemon"],
+    ["autostart", "status"],
 ]
 
 
@@ -141,7 +142,8 @@ def test_the_verb_list_here_matches_the_parser():
 
 
 @pytest.mark.skipif(sys.platform == "win32",
-                    reason="systemd lifecycle; Windows path (schtasks) is W3, not built")
+                    reason="systemd lifecycle; Windows uses the loopback API / "
+                           "Startup-folder launcher, covered by test_platform.py")
 @pytest.mark.parametrize("argv,verb", [
     (["reload"], "reload"),
     (["restart-daemon"], "restart"),
@@ -170,7 +172,8 @@ def test_lifecycle_commands_delegate_to_systemctl_user(
 
 
 @pytest.mark.skipif(sys.platform == "win32",
-                    reason="systemd lifecycle; Windows path (schtasks) is W3, not built")
+                    reason="systemd lifecycle; Windows uses the loopback API / "
+                           "Startup-folder launcher, covered by test_platform.py")
 @pytest.mark.parametrize("argv", [["reload"], ["restart-daemon"]])
 def test_lifecycle_commands_report_systemctl_failure(
         argv, stub_daemon, monkeypatch, capsys):
diff --git a/packages/meshbay-node/tests/test_platform.py b/packages/meshbay-node/tests/test_platform.py
index 9358894..f9464c3 100644
--- a/packages/meshbay-node/tests/test_platform.py
+++ b/packages/meshbay-node/tests/test_platform.py
@@ -102,3 +102,78 @@ def test_configure_event_loop_selector_opt_in(monkeypatch):
     plat.configure_event_loop()
     assert isinstance(asyncio.get_event_loop_policy(),
                       asyncio.WindowsSelectorEventLoopPolicy)
+
+
+# ── Autostart ────────────────────────────────────────────────────────────────
+#
+# On Windows autostart is a `.vbs` in the per-user Startup folder (a logon task
+# would need elevation). Tests point APPDATA at a tmp dir so the real Startup
+# folder is never touched, and force sys.platform.
+
+@pytest.fixture
+def win_startup(monkeypatch, tmp_path):
+    monkeypatch.setattr(sys, "platform", "win32")
+    monkeypatch.setenv("APPDATA", str(tmp_path))
+    return (tmp_path / "Microsoft" / "Windows" / "Start Menu" / "Programs"
+            / "Startup" / "MeshBay Node.vbs")
+
+
+def test_autostart_supported_tracks_the_platform(monkeypatch):
+    monkeypatch.setattr(sys, "platform", "win32")
+    assert plat.autostart_supported() is True
+    monkeypatch.setattr(sys, "platform", "linux")
+    assert plat.autostart_supported() is False
+
+
+def test_autostart_status_is_inert_off_windows(monkeypatch):
+    monkeypatch.setattr(sys, "platform", "linux")
+    assert plat.autostart_status() == {"installed": False, "state": ""}
+
+
+def test_autostart_install_writes_a_hidden_launcher_in_the_startup_folder(win_startup):
+    exe = r"C:\Program Files\MeshBay\meshbay-node.exe"
+    plat.autostart_install(exe=exe)
+
+    assert win_startup.exists()
+    assert plat.autostart_status() == {"installed": True, "state": ""}
+    raw = win_startup.read_bytes()
+    assert b"\r\n" in raw and b"\n\n" not in raw          # CRLF, no stray LF
+    text = raw.decode("utf-8")
+    assert f'"{exe}"' in text                             # path is quote-wrapped
+    assert "Chr(34)" in text and ", 0, False" in text     # hidden, non-blocking
+
+
+def test_autostart_remove_deletes_the_launcher_and_is_idempotent(win_startup):
+    plat.autostart_install(exe=r"C:\x\meshbay-node.exe")
+    assert win_startup.exists()
+    plat.autostart_remove()
+    assert not win_startup.exists()
+    plat.autostart_remove()                               # no error second time
+
+
+def test_autostart_install_needs_a_locatable_launcher(win_startup, monkeypatch):
+    monkeypatch.setattr(plat, "_node_exe", lambda: None)
+    with pytest.raises(RuntimeError, match="locate the meshbay-node launcher"):
+        plat.autostart_install()
+
+
+def test_autostart_install_refuses_off_windows(monkeypatch):
+    monkeypatch.setattr(sys, "platform", "linux")
+    with pytest.raises(RuntimeError, match="Windows-only"):
+        plat.autostart_install(exe="/usr/bin/meshbay-node")
+
+
+def test_autostart_run_launches_the_resolved_exe_detached(win_startup, monkeypatch):
+    monkeypatch.setattr(plat, "_node_exe", lambda: r"C:\x\meshbay-node.exe")
+    calls = {}
+    monkeypatch.setattr(plat.subprocess, "Popen",
+                        lambda argv, **kw: calls.update(argv=argv, kw=kw))
+    plat.autostart_run()
+    assert calls["argv"] == [r"C:\x\meshbay-node.exe"]
+    assert calls["kw"]["creationflags"] & 0x08000000      # CREATE_NO_WINDOW
+
+
+def test_autostart_run_refuses_off_windows(monkeypatch):
+    monkeypatch.setattr(sys, "platform", "linux")
+    with pytest.raises(RuntimeError, match="Windows-only"):
+        plat.autostart_run()