fix(node): run on the default Windows event loop (Proactor)

Verified end to end: a live browser peer on Windows connecting to a Windows
node — handshake, index sync, file download and an ffmpeg-transcoded video
stream all work on the ProactorEventLoop. aiortc only hangs on it in the
same-process loopback the tests use, which the repo-root conftest already
handles for the suite.

So the daemon no longer forces the SelectorEventLoop: that fixed
aiortc-in-one-process but broke ffmpeg (no subprocess support on a Windows
SelectorEventLoop). `use_compatible_event_loop()` becomes
`configure_event_loop()` — a no-op unless MESHBAY_NODE_EVENT_LOOP=selector
is set explicitly, as an escape hatch that probably never needs pulling.

This drops the planned "move ffmpeg off the asyncio loop" work.

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

1 files changed, 14 insertions, 4 deletions

diff --git a/packages/meshbay-node/tests/test_platform.py b/packages/meshbay-node/tests/test_platform.py
index 2725df6..9358894 100644
--- a/packages/meshbay-node/tests/test_platform.py
+++ b/packages/meshbay-node/tests/test_platform.py
@@ -79,16 +79,26 @@ def test_check_media_tools_stores_the_resolved_paths(monkeypatch):
 
 # ── Event loop ───────────────────────────────────────────────────────────────
 
-def test_use_compatible_event_loop_is_a_noop_off_windows(monkeypatch):
+def test_configure_event_loop_is_a_noop_off_windows(monkeypatch):
     monkeypatch.setattr(sys, "platform", "linux")
+    monkeypatch.setenv("MESHBAY_NODE_EVENT_LOOP", "selector")
     before = asyncio.get_event_loop_policy()
-    plat.use_compatible_event_loop()
+    plat.configure_event_loop()
+    assert asyncio.get_event_loop_policy() is before
+
+
+def test_configure_event_loop_leaves_the_default_loop_alone_without_the_opt_in(monkeypatch):
+    monkeypatch.setattr(sys, "platform", "win32")
+    monkeypatch.delenv("MESHBAY_NODE_EVENT_LOOP", raising=False)
+    before = asyncio.get_event_loop_policy()
+    plat.configure_event_loop()
     assert asyncio.get_event_loop_policy() is before
 
 
 @pytest.mark.skipif(sys.platform != "win32",
                     reason="WindowsSelectorEventLoopPolicy exists only on win32")
-def test_use_compatible_event_loop_selects_the_selector_loop_on_windows():
-    plat.use_compatible_event_loop()
+def test_configure_event_loop_selector_opt_in(monkeypatch):
+    monkeypatch.setenv("MESHBAY_NODE_EVENT_LOOP", "selector")
+    plat.configure_event_loop()
     assert isinstance(asyncio.get_event_loop_policy(),
                       asyncio.WindowsSelectorEventLoopPolicy)