Prepare pipewire-gobject 0.3.6 release

[bhack]

Summary

• add explicit sync helpers for core, registry, metadata, node, and device wrappers
• add request-scoped sync enum params helpers for node and device params
• add release metadata consistency checks and clang-tidy CI coverage

Validation

• docker release gate: metadata, normal tests, fatal-warning tests, docs build, clang-tidy, ruff, strict build/tests, sanitizer/UBSan tests
• Meson dist archive test
• Python sdist/wheel build plus twine check
• wheel import smoke reports Pwg 0.3.6
• temporary PipeWire live smoke via tests/test_live_pipewire.py