ci: Run all test groups in CI, including integration tests

[dean0x]

Problem

CI currently skips several test groups: scheduling, checkpoints, CLI, integration tests, and worker-handler. This means regressions in these areas go undetected until local testing.

Scope

1. Audit ci.yml to identify which test groups are missing
2. Add missing test groups to the CI matrix/steps:
   • npm run test:cli
   • npm run test:integration
   • npm run test:worker-handler (try with 4GB heap — CI runners have 7GB)
3. Investigate whether integration tests truly require the claude binary (they use mocks — likely don't)
4. Consider running test groups as a matrix strategy for parallel execution
5. Ensure CI still completes in reasonable time (<10 minutes)

Acceptance Criteria

• All test groups run in CI
• CI passes on main
• No test group is silently skipped
• CI completes in <10 minutes

Dependencies

• Depends on Vitest 4 upgrade (memory behavior may change, affecting CI resource needs)

[dean0x]

Resolved in PR #58. CI now uses npm run test:all instead of ad-hoc test steps.