Implement Ava orchestrator: spawn and monitor pi subprocesses

Implement the core orchestration logic in Ava to spawn and monitor pi-orchestrate.sh.

Simplified Approach

Use the bash scripts directly instead of waiting for Haskell conversion:

• Spawn pi-orchestrate.sh as subprocess
• Parse stdout for progress updates
• Report to Telegram

Implementation

Core Types

data WorkerState
  = Idle
  | Working TaskId ProcessHandle ThreadId  -- task, process, output reader
  | Failed TaskId Text

data OrchestratorEvent
  = StartTask TaskId
  | WorkerOutput Text      -- line from stdout
  | WorkerFinished ExitCode
  | UserMessage Text

Subprocess Management

1. Spawn pi-orchestrate.sh with task ID 2. Fork thread to read stdout line by line 3. Parse key lines (phase changes, completion) 4. Send Telegram updates at key points 5. Handle completion/failure

Integration Points

• Omni.Agent.Telegram: send messages, receive commands
• Omni.Task.Core: task lookup for validation
• System.Process: subprocess spawning

Error Handling

• Subprocess crash: notify user, mark needs-help
• Timeout: kill subprocess, notify user
• Task not found: error message
• Already working: queue or reject

Files

• Omni/Agent/Telegram/Orchestrator.hs (new)
• Omni/Agent/Telegram.hs (wire up commands)