[leecyang]

Release v2.3.0

Prepare the LingxiGraph 2.3.0 production release focused on durable mid-run steering.

Versioning

• bump Python package metadata to 2.3.0
• bump runtime __version__ to 2.3.0
• align Helm chart/appVersion to 2.3.0
• finalize the 2.3.0 - 2026-08-18 CHANGELOG section

Release notes

Adds a standard GitHub Release introduction covering:

• durable /steer API and Python SDK
• application-controlled safe points
• PostgreSQL durability and retry semantics
• pause/resume lineage and cancellation correctness
• worker fencing and lifecycle observability
• PostgreSQL migration requirements through 0005_superseded_by_run_id
• compatibility and installation guidance

Publishing

Hardens .github/workflows/publish.yml into a standard release pipeline:

1. a version bump merged to main creates an annotated v2.3.0 tag
2. distributions are built and metadata-verified in a read-only build job
3. artifacts are passed to a dedicated PyPI Trusted Publishing job via OIDC
4. after a successful PyPI upload, a GitHub Release is created and the wheel/sdist are attached
5. manual workflow_dispatch remains available for TestPyPI or recovery publishing

The build and OIDC publish stages are deliberately separated, following PyPA's Trusted Publishing guidance.

No new Runtime behavior is introduced by this PR; it packages and publishes the already-merged 2.3.0 functionality.