ci(governance): exempt release-please PRs from PR-body template

[krisarmstrong]

Summary

release-please PRs carry an auto-generated changelog body, which fails the required Lint PR Body check (missing the human-PR headings + single linked issue), permanently blocking releases under enforce_admins. Exempt release-please--* branches from the human-template validation — branch-based since the release-PR author varies by token.

Linked Issue

Related to #488

Testing Evidence

actionlint .github/workflows/pr-body-lint.yml -> clean
The Validate-PR-body step now has: if: github.event_name == 'pull_request' && !startsWith(github.head_ref, 'release-please--')
Job still reports success for release PRs (only-applicable step skipped, nothing fails).

Security and Release Checklist

• No secrets, tokens, credentials, or customer data are included.
• Mutating routes, auth surfaces, permission checks, and output encoding were reviewed if touched.
• Dependencies are pinned and justified if changed.
• Documentation, screenshots, or operator notes were updated if behavior changed.

[github-actions]

License Compliance Report

All dependencies pass license compliance checks

Go Dependencies

• Unknown: 35 package(s)
• MIT: 26 package(s)
• BSD-3-Clause: 16 package(s)
• Apache-2.0: 11 package(s)
• BSD-2-Clause: 1 package(s)

npm Dependencies

See full report in workflow artifacts

Allowed Licenses: MIT, Apache-2.0, BSD-*, ISC, CC0-1.0, MPL-2.0
Forbidden: GPL, AGPL, SSPL (strong copyleft)