[Bug] Agent response truncated - NoneType subscriptable error

## Bug Description

### Problem
The AI agent's response is frequently being truncated mid-sentence, with the error message:
```
[Compactor] failed: 'NoneType' object is not subscriptable
```

This happens consistently when generating longer responses (typically after 400-600 lines of content).

### Frequency
- Occurs in approximately 30-50% of longer responses
- More frequent when writing files, running shell commands, or content exceeds ~500 lines

### Impact
- User workflow is frequently interrupted
- Cannot complete complex documentation tasks
- Wastes token quota on repeated attempts

## Environment
- OS: Darwin 25.3.0 (macOS)
- CoPaw Version: 1.0.1

## Error Details
```
[Compactor] failed: 'NoneType' object is not subscriptable
```

## Expected Behavior
1. Agent should generate long responses without truncation
2. If truncation is necessary, complete current thought first
3. Compactor should handle None values gracefully

## Suggested Fix
Check the Compactor code path for subscript operations without None checks, response buffer management, and token counting logic.