fix: make release PR checks explicit

[mktbsh]

Summary

• use a maintainer-authored empty commit to trigger required Release PR checks
• remove the ineffective manual-dispatch path
• update CI Actions to their Node 24-based major versions
• record the token-free release decision and lesson

Validation

• actionlint
• pnpm run docs:check
• pnpm run release:config:check
• git diff --check