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>

1 files changed, 88 insertions, 0 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/platform.py b/packages/meshbay-node/src/meshbay_node/platform.py
index 351289f..b59418f 100644
--- a/packages/meshbay-node/src/meshbay_node/platform.py
+++ b/packages/meshbay-node/src/meshbay_node/platform.py
@@ -3,6 +3,7 @@
 import asyncio
 import os
 import shutil
+import subprocess
 import sys
 from pathlib import Path
 
@@ -109,3 +110,90 @@ def ffmpeg_cmd() -> str:
 
 def ffprobe_cmd() -> str:
     return _ffprobe_path
+
+
+# ── Autostart (Windows) ──────────────────────────────────────────────────────
+#
+# The Windows stand-in for the Linux `systemctl --user` unit. Task Scheduler
+# would be nicer (retry semantics), but a logon-triggered task needs elevation
+# to create — and this must work for an ordinary user with no admin rights.
+# So: a `.vbs` launcher in the per-user Startup folder. wscript runs it hidden
+# (Run(..., 0, ...)) at every sign-in; no console window, no admin, no
+# third-party dependency.
+
+TASK_NAME = "MeshBay Node"   # the name the Electron client shows
+
+
+def autostart_supported() -> bool:
+    return sys.platform == "win32"
+
+
+def _startup_vbs() -> Path:
+    base = os.environ.get("APPDATA") or str(Path.home() / "AppData" / "Roaming")
+    return (Path(base) / "Microsoft" / "Windows" / "Start Menu" / "Programs"
+            / "Startup" / "MeshBay Node.vbs")
+
+
+def _node_exe() -> str | None:
+    """Best guess at the meshbay-node launcher: PATH first, then next to the
+    interpreter (a venv's Scripts/ dir, or a bundled runtime), then argv[0]."""
+    found = shutil.which("meshbay-node")
+    if found:
+        return found
+    for cand in (Path(sys.executable).parent / "meshbay-node.exe",
+                 Path(sys.argv[0])):
+        if cand.name.lower().startswith("meshbay-node") and cand.exists():
+            return str(cand.resolve())
+    return None
+
+
+def autostart_status() -> dict:
+    """{'installed': bool, 'state': str}. 'state' is left empty — there is no
+    Task Scheduler to ask 'is it running'; the Node page probes the daemon."""
+    if not autostart_supported():
+        return {"installed": False, "state": ""}
+    return {"installed": _startup_vbs().exists(), "state": ""}
+
+
+def autostart_install(exe: str | None = None) -> None:
+    """Write the Startup-folder launcher. Raises RuntimeError on failure."""
+    if not autostart_supported():
+        raise RuntimeError("autostart is Windows-only")
+    exe = exe or _node_exe()
+    if not exe:
+        raise RuntimeError(
+            "cannot locate the meshbay-node launcher — pass its path, or run "
+            "this from where meshbay-node is on PATH")
+    vbs = _startup_vbs()
+    vbs.parent.mkdir(parents=True, exist_ok=True)
+    # Chr(34) is a literal " — wraps the path so a space in it doesn't split the
+    # command. 0 = hidden window, False = don't wait. (A Windows path cannot
+    # itself contain ", so no further escaping is needed.)
+    vbs.write_text(
+        f'CreateObject("WScript.Shell").Run Chr(34) & "{exe}" & Chr(34), 0, False\n',
+        encoding="utf-8", newline="\r\n")
+
+
+def autostart_remove() -> None:
+    """Delete the Startup-folder launcher if present."""
+    if autostart_supported():
+        _startup_vbs().unlink(missing_ok=True)
+
+
+def autostart_run() -> None:
+    """Start the daemon now, detached and windowless. Raises RuntimeError if
+    the launcher cannot be located."""
+    if not autostart_supported():
+        raise RuntimeError("autostart is Windows-only")
+    exe = _node_exe()
+    if not exe:
+        raise RuntimeError("cannot locate the meshbay-node launcher")
+    subprocess.Popen([exe], creationflags=0x00000008 | 0x08000000,  # DETACHED | NO_WINDOW
+                     close_fds=True)
+
+
+def autostart_end() -> None:
+    """Stop any running daemon (hard: there is no CTRL_CLOSE handler yet)."""
+    if autostart_supported():
+        subprocess.run(["taskkill", "/IM", "meshbay-node.exe", "/F"],
+                       capture_output=True)