feat: update tests for Amp SDK agent integration

[rubenmarcus]

Summary

Add unit and integration tests for Amp SDK agent support.

Linear: ENG-1466

Test Coverage

1. Agent detection: detectAgent() correctly identifies Amp when installed
2. Agent invocation: runAgent() spawns Amp with correct parameters
3. Output parsing: Amp's stream format parsed correctly
4. Mode switching: smart/rush/deep modes configured correctly
5. Loop execution: Full loop with Amp agent completes successfully
6. Error handling: Amp failures handled gracefully

Files

• tests/agents.test.ts (or create new)
• tests/executor.test.ts

Depends On

• Issue L (Agent abstraction)
• Issue M (Executor support)
• Issue O (Config + flags)