Window-level PrintWindow/mss returns blank on GPU-accelerated apps
(TradeStation, some trading terminals). Switch to full-desktop screenshot
+ drag-rectangle as the default method — reliable across all apps.
- Title prompt still asked (needed by 'atm run' to locate window at runtime).
- Captured region saved to logs/calibrate_capture_<ts>.png for verification.
- Old window-capture path kept as fallback if region-select is cancelled.
- Minor: silence pyright windll attr warning.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
