fix(ci): allow release branch scopes in PR title validation (#349)

## Summary

- Adds `release/v0\.\d+` regex pattern to the allowed scopes in the PR
title validation workflow
- Fixes `Validate PR title` check failing on release-please PRs
targeting release branches (e.g. #348, #315, #289)

Release-please uses the pattern `chore(${branch}): release ${version}`
for PR titles, which produces scopes like `release/v0.13` for release
branch PRs. These scopes were not in the allowed list, causing CI to
fail.

## Test plan

- [x] Verify this PR's own `Validate PR title` check passes
- [ ] Confirm #348 passes after this merges (or re-run its check)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Enhanced pull request validation workflow to recognize and properly
handle release automation processes.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Mary Dickson <mary.dickson@virtru.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: marythought

.github/workflows/checks.yaml

@@ -49,6 +49,7 @@ jobs:
           #   - sdk: changes to sdk
           #   - tests: test only changes
           #   - examples: examples only changes
+          #   - release/v0.\d+: release-please release branch PRs
           scopes: |
             ci
             cmdline
@@ -57,6 +58,7 @@ jobs:
             sdk
             tests
             examples
+            release/v0\.\d+
 
   mavenverify:
     runs-on: ubuntu-latest