Stabilize CI run tests and fix timeout-hang root cause

[eve-senara]

Summary

• fix timeout/hang in run command tests by removing fragile setup module mock path
• set deterministic OPENAI_API_KEY in run test harness beforeEach/afterEach
• keep task-runner test deterministic by stubbing executeTask in failed-status path

Validation

• npm run lint
• npm run lint:type-aware
• npm run typecheck
• npm run test
• npm run build
• npm run validate
• bun test src/core/task-runner.test.ts
• bun test src/cli/commands/run.test.ts
• bun test src/cli/commands/run.postexec-json.integration.test.ts

[github-actions]

No issues found. This PR stabilizes CI test determinism by properly setting/restoring OPENAI_API_KEY in the run command test harness and adding a setExecuteTaskForTests stub to prevent non-deterministic behavior in the cyclic-task failure test path.