Split screen boundary usage into two sources:
1. walk / roam / run-to-target (unchanged):
- self.screen_* = WindowManager.get_work_area() (primary monitor, taskbar-aware)
- Cat autonomously roams the primary desktop floor only
2. drag clamping (new):
- self.vd_* = WindowManager.get_virtual_desktop_bounds() (all monitors)
- on_mouse_move() clamps to vd_left/right/top/bottom instead of
screen_left/right/top/bottom
- User can now pick up the cat and drag it to any connected monitor
Previously on_mouse_move() clamped to the primary work area rectangle
(0, 0, 1920, 1032), so moving the cursor past x=1776 would immediately
snap the cat back, making the second monitor unreachable.
_premultiply_bgra() was iterating over every RGBA pixel in a pure-Python
for-loop at 60 FPS (144x110 sprite = ~950k iterations/sec). This was the
primary cause of UI hangs.
New implementation uses numpy:
- np.frombuffer + reshape to view raw bytes as (H*W, 4) uint8 array
- Fancy-index column reorder [2,1,0,3] for R,G,B,A -> B,G,R,A in one op
- float32 alpha / 255 premultiplication via broadcasting
- tobytes() to emit the final DIB data
Roughly 100x faster than the previous loop, freeing the main thread to
sustain 60 FPS without freezing.