ci: sync shared workflow callers

[damacus]

Summary

• Use the current shared Conventional Commit caller contract.
• Pass the Slack secrets required by release workflow 9.0.0.
• Restore workflow startup before the next merge to main.

Verification

• actionlint on both changed workflows
• yamllint on both changed workflows
• git diff --check

[github-actions]

Slowest examples

Top 3 slowest examples (0.07 seconds, 100% of total time)

Example	Description	Time in seconds
spec/resources/install_spec.rb:12	chruby_install install chruby	0.03301
spec/resources/install_spec.rb:13	chruby_install install chruby	0.02182
spec/resources/install_spec.rb:23	chruby_install on Amazon Linux	0.01848

[damacus]

Note for future self

changes to the "conventional-commits" workflow:

1. Keep the "synchronize" trigger. We want this validation to rerun whenever new commits are pushed or the PR head is otherwise updated. The trigger should remain:

   types: [opened, edited, reopened, synchronize]

2. Review "secrets: inherit". This workflow appears to require only "pull-requests: read". If the reusable "sous-chefs/.github/.github/workflows/conventional-commits.yml@9.0.0" workflow does not explicitly require secrets, remove "secrets: inherit". We should avoid exposing repository secrets to a "pull_request_target" workflow unnecessarily.

Keep the switch to "pull_request_target"; this is PR-metadata validation and needs to work reliably for fork PRs.