What

Add pull_request trigger to the Doxygen documentation workflow.

• Current: network_system's build-Doxygen.yaml triggers only on push to main and workflow_dispatch. PRs do not trigger a Doxygen build, so documentation-breaking changes are not caught before merge.
• Expected: PRs also trigger the Doxygen build (build-only, no deployment) to catch documentation issues early.
• Scope: .github/workflows/build-Doxygen.yaml trigger section

Why

• All other libraries include PR triggers: common, thread, logger, container, monitoring, database all trigger on pull_request. network_system is the only exception.
• Documentation regressions: Without PR validation, Doxygen warnings or errors from header changes are only discovered after merge to main.
• No risk: The shared workflow already guards deployment with if: github.event_name == 'push' && github.ref == 'refs/heads/main', so PR runs only build — they never deploy.

Where

How

Current

on:
  push:
    branches: [main]
  workflow_dispatch:

Target

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]
  workflow_dispatch:

Acceptance Criteria

• pull_request trigger added to build-Doxygen.yaml
• PR builds run Doxygen without deploying
• Push to main still triggers build + deploy as before