ci: harden github actions workflows against zizmor warnings

[timothyfroehlich]

Description

This PR implements security hardening across all GitHub Actions workflows in the repository to align with modern security best practices and prevent potential supply chain or CI/CD vulnerabilities.

Changes

1. Enforce Principle of Least Privilege (Granular Permissions):

   • Added explicit top-level permissions blocks to all workflows to restrict the default scope of the GITHUB_TOKEN.
   • Restricted all workflows to contents: read by default.
   • Granted pull-requests: read only to the CI workflow, which is specifically required by dorny/paths-filter to fetch file diffs via the GitHub API for pull requests.

2. Disable Git Credential Persistence:

   • Set persist-credentials: false on all actions/checkout steps across all 5 workflows. This ensures the GITHUB_TOKEN is not stored in the runner's local Git configuration, preventing subsequent build steps or third-party actions from accessing it.

3. Add Concurrency Controls:

   • Configured top-level concurrency groups in entrypoint workflows (ci.yml and generate_release_rcs.yml) to automatically cancel in-progress runs when new commits are pushed to the same branch or pull request.

4. Secure Matrix Variable Expansion (Shell Injection Prevention):

   • Updated oss-licenses.yml to pass matrix variables (e.g., ${{ matrix.agp-version-key }}) into steps via step-level env blocks instead of interpolating them directly into inline shell script run strings. This ensures the values are handled safely as data rather than executable code.

5. Improve UI Readability:

   • Added descriptive, human-readable name: fields to all jobs across the workflows to improve the structure and readability of the GitHub Actions run UI.

Verification

• Verified locally using the zizmor static analysis linter with the most sensitive auditing profile (--persona=auditor --min-severity=informational --min-confidence=low), reporting 0 findings.