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, 19 insertions, 0 deletions

diff --git a/packages/meshbay-node/tests/conftest.py b/packages/meshbay-node/tests/conftest.py
index 03dfb42..20724aa 100644
--- a/packages/meshbay-node/tests/conftest.py
+++ b/packages/meshbay-node/tests/conftest.py
@@ -1,9 +1,28 @@
 """Shared fixtures and helpers for node tests."""
 
+import sys
 from pathlib import Path
 
+import pytest
 from meshbay_node.roots import RootSet
 
+# ffmpeg / ffprobe run via asyncio.create_subprocess_exec, which needs the
+# ProactorEventLoop — but the repo-root conftest forces the SelectorEventLoop
+# on win32 so aiortc's ICE stack works there (see devel/windows-devel.md §5).
+# The two are mutually exclusive on one Windows asyncio loop; until the media
+# path gets a thread-based subprocess runner, these tests can't run on win32.
+needs_subprocess = pytest.mark.skipif(
+    sys.platform == "win32",
+    reason="ffmpeg subprocess needs ProactorEventLoop; win32 conftest forces "
+           "SelectorEventLoop for aiortc",
+)
+
+# Windows-only gaps still to close (see devel/windows-devel.md §5/§6).
+win32_todo = pytest.mark.skipif(
+    sys.platform == "win32",
+    reason="Windows behaviour not implemented yet (W3 / platform specifics)",
+)
+
 
 def one_root(path: Path, *, name: str = "", kind: str = "generic") -> RootSet:
     """