Layout persistence: re-enable io.IniFilename (was nullptr "for the spike"),
anchored to a coop_layout.ini next to the exe so window positions/sizes survive
restarts even when Steam launches us under the donor appid (CWD is unreliable).
Path is UTF-8 for ImGui's file IO. When a saved layout is restored at startup,
suppress the computed-default force so it does not clobber the user's positions;
Reset layout (and a fresh install with no .ini) still applies the default.
Log spam: the worker thread re-attaches every audio ring every tick (idempotent),
and set_audio_ring logged unconditionally, flooding the log. Only log when the
ring pointer actually changes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>