feat: automate SyncField version bump and PyPI release

[Skyrich2000]

What changed

• require Python 3.12+ and validate on Python 3.12/3.13
• keep pull-request CI focused on viewer build and Python tests
• add an idempotent bump job that maps PR title prefixes to SemVer (major → major, feat: → minor, otherwise patch)
• commit pyproject.toml and uv.lock with [skip ci] and a source-PR marker
• add a dependent release job that builds/verifies distributions, tags the release commit, publishes through PyPI Trusted Publishing, and creates a GitHub Release
• support manual retry by merged PR number without double-bumping or failing on an existing PyPI version

First release

This PR deliberately keeps the repository version at the current PyPI version, 0.6.0. Because the PR title starts with feat:, merging it will exercise the new CD and publish 0.7.0.

Validation

• bump-version tests: 2 passed
• Ruff on the bump script/tests: passed
• full suite: 1,252 passed, 2 skipped; one parallel multihost socket test failed under xdist and passed immediately when rerun alone
• workflow YAML parse and git diff --check: passed