fix(release): accept exact generated merge title

[chhoumann]

Summary

• Accept the exact generated release merge subject as well as the matching GitHub-added PR suffix.
• Keep the release PR title, parent, tree, changed-file, author, merger, branch, and provenance checks unchanged.
• Execute the inline validators from both release workflows in behavioral contract tests.

Why

Release PR #265 used the exact generated title, as required by the repository release instructions, but GitHub produced an unsuffixed squash subject. The prior workflow accepted only the suffixed form, so the validated 2.18.0 commit merged successfully but publication did not start.

Validation

• fnm exec --using=22 -- npm run test -- scripts/release-contract.test.ts scripts/release-plan.test.ts scripts/release-workflow-contract.test.ts
• fnm exec --using=22 -- npm run format:check
• fnm exec --using=22 -- npm run lint
• fnm exec --using=22 -- npm run typecheck
• Parsed all six workflow YAML files
• git diff --check

Obsidian runtime verification was not performed because this change only affects GitHub release workflow validation.

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