ci: align branch governance and audit workflow

[roger-gan]

Description

Align branch governance for main and develop, and disable automatic PR
Audit by default while the self-hosted runner is unavailable. Manual
/audit-pr requests remain available to authorized users.

Tests

• Parsed .github/workflows/audit-pr.yml successfully with Ruby YAML.
• Ran git diff --check.
• Verified the effective GitHub Ruleset on both main and develop.

Branch route

• Normal development targets develop
• Only release_* or hotfix/* targets main

Checklist

• I have formatted and linted my code
• All new and existing tests pass
• I added a Changeset for publishable package changes, or this PR does not require one
• My commits are signed (required for merge) -- you may need to rebase if you initially pushed unsigned commits