Recover routed streams after PipeWire relink

[bhack]

Summary

• schedule a stream-router refresh when an already-routed stream is relinked away from Mini EQ or loses its current link
• extend native and Flatpak runtime smokes with paused, recreated, and forced-relink stream phases
• harden the runtime smoke setup around WirePlumber default-device races

Refs #27.

Validation

• .venv/bin/python -m pytest tests/test_mini_eq_pipewire_stream_router.py tests/test_check_flatpak_runtime.py tests/test_check_headless_pipewire_runtime.py tests/test_check_live_ui_runtime.py tests/test_github_workflows.py tests/test_release_preflight.py -q
• .venv/bin/python tools/check_headless_pipewire_runtime.py --timeout 80 --cycles 1 --idle-gap 6
• MINI_EQ_FLATPAK_BUILD=1 MINI_EQ_FLATPAK_APP_REF=io.github.bhack.mini-eq//master ... tools/run_flatpak_runtime_smoke_ci.sh
• released Flathub 0.8.1 fails the new relink phase, while the local Flatpak build from this branch passes it

Notes

This is intentionally draft until the issue reporter can stress-test the Flathub CI build with the original Chrome/YouTube workflow.