When the scout agent fails (e.g., context window exhaustion), now:
- Captures both stdout and stderr from the scout process
- Detects context window exhaustion errors with specific patterns
- Provides detailed, actionable error messages to the user
- Shows suggestions for how to work around the issue
- Includes technical details (exit code, error output) for debugging
Handles two failure modes:
1. Scout agent exits with non-zero status
2. Scout agent exits successfully but doesn't produce valid report markers
Both cases now surface clear error messages instead of cryptic failures.