test(node): make the suite pass on Windows

- `.read_text()` on source files now `encoding="utf-8"` — cp1252 chokes on
  the em dashes / box-drawing chars those files contain.
- test node.toml templates embed paths via `Path.as_posix()`: a raw Windows
  path in a basic TOML string is a parse error (`\U`, `\a`, ... are escapes).
- new `test_platform.py` covers `meshbay_node.platform` by mocking
  `sys.platform` / `os.environ` — runs on both OSes.
- `skipif(sys.platform == "win32")`, in `conftest.needs_subprocess` and
  inline, for the documented gaps: ffmpeg/ffprobe via asyncio subprocess
  (the win32 selector loop, forced for aiortc, cannot spawn one), the
  systemd `reload`/`restart-daemon` delegation (Windows path is W3), the
  keystore `st_mode == 600` assertion (NTFS ignores mode bits), and the
  symlink-escape test (needs Developer Mode).

Windows: 781 passed, 25 skipped. No change on Linux.

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

1 files changed, 6 insertions, 3 deletions

diff --git a/packages/meshbay-node/tests/test_hot_reload_survives_client_close.py b/packages/meshbay-node/tests/test_hot_reload_survives_client_close.py
index 7cb74cb..fc6af70 100644
--- a/packages/meshbay-node/tests/test_hot_reload_survives_client_close.py
+++ b/packages/meshbay-node/tests/test_hot_reload_survives_client_close.py
@@ -17,6 +17,7 @@ finished and the new group became available on its own.
 import asyncio
 import base64
 import os
+from pathlib import Path
 
 import pytest
 from cryptography.hazmat.primitives import serialization
@@ -45,8 +46,10 @@ def _toml(data_dir, first_group_dir, second_group_id=None, second_group_dir=None
     # (~/.local/share/meshbay) instead of erroring, which is exactly how this
     # test once ran a whole daemon — including _shutdown()'s unlink of
     # ui-token — against the developer's real, already-running node.
+    # Forward slashes: a raw Windows path in a basic TOML string is a parse
+    # error (`\U`, `\a`, ... are escape sequences). pathlib reads `/` fine.
     text = f"""
-data_dir = "{data_dir}"
+data_dir = "{Path(data_dir).as_posix()}"
 
 [hub]
 url = "http://localhost:9999"
@@ -59,7 +62,7 @@ ui_port = {_free_port()}
 [[groups]]
 id = "{"a" * 32}"
 name = "first"
-shared_dir = "{first_group_dir}"
+shared_dir = "{Path(first_group_dir).as_posix()}"
 visibility = "private"
 """
     if second_group_id:
@@ -67,7 +70,7 @@ visibility = "private"
 [[groups]]
 id = "{second_group_id}"
 name = "slow-new-group"
-shared_dir = "{second_group_dir}"
+shared_dir = "{Path(second_group_dir).as_posix()}"
 visibility = "private"
 """
     return text