chore(ci): migrate actions to Node 24 runtime

[ClaudiaFang]

Tracks firstsun-dev/.github#29

Upgraded actions

• dorny/paths-filter v3 → v4 (SHA-pinned: ceb8a2b8f2d8… # v4)

Why

GitHub is deprecating the Node.js 20 runtime for JavaScript actions; the previous versions declare runs.using: node20. The new versions declare node24 (verified in each upstream action.yml).

Validation

• YAML parses for all workflows; actionlint run on changed files — only pre-existing findings unrelated to the changed lines
• Grep confirms no remaining targeted old action versions
• git diff is minimum-diff (only uses: lines)
• Workflow-only change; no application tests affected

Compatibility notes

• filters/outputs untouched. Other jobs use self-hosted runners (already on checkout@v6).

Behavior

No workflow or application behavior was intentionally changed (runners, permissions, secrets, env, triggers, concurrency, job deps, app Node/Python versions untouched).

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud