audio: call pw_loop_enter/leave on the SPA event loop

[zhouwg]

Overview

PwCore::start() creates a pw_loop but never calls pw_loop_enter() before iterating it via QSocketNotifier. This triggers SPA's internal assertion impl->enter_count > 0 at loop.c:817 on every pw_loop_iterate() call, causing the PipeWire connection to fail silently.

Add pw_loop_enter() after pw_loop_new() and pw_loop_leave() before pw_loop_destroy() to properly manage the loop lifecycle.

Additional information

Before the fix: clicking the audio icon had no response, and audio volume adjustment did not work.
After the fix: audio volume adjustment works correctly.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: Yes, Paired with MiMoCode + MiMo-V2.5-Pro, use MiMo-V2.5-Pro to generate the fix, then reviewed/tested manually.

[outfoxxed]

Its unclear if we should enter this when processing pipewire events (from socket notify) or just for the full duration of the connection and there is zero documentation (as usual). I also don't get this so I guess they changed an assertion in a newer package version than I'm on.

Did you try both positions or know why it should go around the app event loop vs event stream handling?

[outfoxxed]

Did some research, looks correct.

Can you enable maintainer edits on the branch?