Consolidate and clarify pre-merge check workflows

[ashleyshaw]

Summary

Linting and testing are split across multiple workflows (linting.yml, meta.yml, testing.yml) with unclear trigger logic. This creates confusion about when checks run and risks redundant or competing runs.

Problem

• Triggers scattered across multiple files
• Unclear precedence or order of execution
• Potential for redundant runs (e.g., linting runs twice)
• Concurrency groups not fully specified
• Documentation doesn't explain workflow topology

Solution

Create unified checks.yml workflow that:

1. Consolidates pre-merge checks: lint + test + validate
2. Clear trigger: pull_request and push (develop branch only)
3. Use concurrency groups to prevent overlapping runs
4. Keep meta.yml separate (different cadence: post-push, not pre-merge)
5. Document trigger precedence in comments
6. Add workflow topology diagram to .github/workflows/README.md

Implementation Details

• Effort: 1–2 hours
• Complexity: Low
• Risk: Low (non-breaking refactor)
• Related: Current workflows (linting.yml, testing.yml, meta.yml)
• Dependencies: Existing linting/testing scripts

Acceptance Criteria

• New checks.yml consolidates lint + test + validate
• Existing workflows updated or deprecated with clear migration path
• No regression in check coverage
• Concurrency groups specified and tested
• .github/workflows/README.md documents topology
• CONTRIBUTING.md explains when checks run
• All tests pass

Reference

See workflow standards audit: .github/reports/audits/workflow-standards-audit-2026-05-31.md

[linear-code]

LS-810