Verify the complete release dependency graph in CI

[antono3]

Changes

Verify direct and transitive v.mod dependency pins against installed Git tag commits in required CI. Reject conflicting pins and checkout drift. Leave current-master compatibility lanes advisory.

The helper reads module manifests rather than carrying a second dependency/version list. Companion tags require an explicit selection.

Verification

• Seven positive/negative fixture cases passed with stable V 0.5.2 and pinned V3, including annotated tags, paths containing spaces, transitive drift and conflicting pins.
• Workflow validation passed with actionlint.
• The current release dependency graph passed locally.