Release miniVERL v0.2.3 - #16

Changes

• promote package, changelog and citation metadata from 0.2.3.dev0 to 0.2.3
• freeze the v0.2.3 clarity and defensive-hardening notes
• refresh the pre-tag release checklist and project-state ledger while preserving prior release records

Why

PR #15 is merged and green. A release tag must point at source whose package version, changelog section, citation metadata and checked pre-tag invariants all agree; tagging the development version would be rejected by release.yml.

Impact

This PR changes release metadata only. It does not publish by itself. After this PR is green and merged, the exact merge commit will receive the annotated v0.2.3 tag, which triggers the Trusted Publishing workflow.

Validation

• ruff check ., ruff format --check ., mypy src/miniverl
• 1085 non-GPU/non-network tests passed with 87.30% branch coverage
• exact merged code from PR Harden v0.2.3 clarity and artifact safety #15: 5 GPU tests and 3 network tests passed; 10/10 GitHub checks passed
• clean 0.2.3 wheel and sdist built; twine check passed
• release metadata and all pre-tag checklist items agree at 0.2.3
• frozen benchmark JSON SHA-256 remains 53fc1d4d5b7adee09618d77ad62d4086ba56b78569832d6fc7c3bcd5c2695bbc
• the two v0.2.3 changelog compare URLs are intentionally pre-tag and will resolve when the tag is pushed