Integration tests for agentd pi adapter

Integration tests for agentd pi adapter end-to-end flow.

Test scenarios: 1. Spawn agent → verify running → wait for completion → verify status 2. Spawn agent → send message mid-task → verify received 3. Spawn agent → stop → verify stopped status 4. Spawn multiple agents → verify parallel execution 5. Agent crash → verify failed status and webhook 6. Webhook delivery → verify POST received

Implementation:

• Use tasty for test framework
• Spawn real agentd daemon on test port
• Use mock pi or simple echo agent for fast tests
• Test webhook with local HTTP server

Can be run with: bild --test Omni/Agentd/Daemon.hs