Default to window-based capture resolution; add --width/--height override (fixes #10)

[dffdeeq]

Fix screen capture to default to the game window resolution and correct dxcam region format (fixes #10).

Changes:

• game_env.py: image_width/image_height default to None, so resolved window dimensions are used automatically
• game_env.py: move observation_space initialization after window detection so it uses resolved dimensions
• game_env.py: fix bbox/region format mismatch:
  • dxcam expects (left, top, right, bottom)
  • pyautogui expects (left, top, width, height)
    Previously both were fed the same format, which could result in an invalid region or partial capture.
• play.py: add --width and --height CLI args for manual override

Usage:
automatically uses window resolution:
python scripts/play.py --process game.exe

override with custom resolution:
python scripts/play.py --process game.exe --width 1920 --height 1080

Testing:

• Windows display scaling (DPI): 100%, 125%, 150%
• Tested on multiple window sizes/resolutions (e.g. 1920x1080, 2560x1440)
• Verified dxcam no longer throws "Invalid Region" and captured frames match the full game window

[heliar-k]

I have found that this PR needs to be combined with this modification to work effectively in different DPI scaling ratios when I run the game in window mode.
ra1nty/DXcam#107 (comment)

[dffdeeq]

I have found that this PR needs to be combined with this modification to work effectively in different DPI scaling ratios when I run the game in window mode. ra1nty/DXcam#107 (comment)

is dxcam really seeing a scaled output res on your setup, or is the window just slipping a bit off-screen at high DPI?
On my side dxcam still reports the correct output size even at 200% DPI, and the crash happens when the window/client rect goes out of bounds.

Example where the window fits (works) (image 1):

[WIN] GetWindowRect: (474, 68, 2086, 1326)
[WIN] ClientRect->Screen LTRB: (480, 120, 2080, 1320)

Example where it’s shifted a bit and extends past a 2560x1440 output (fails) (image 2):

[WIN] GetWindowRect: (1006, 260, 2618, 1518)
[WIN] ClientRect->Screen LTRB: (1012, 312, 2612, 1512)

then:

ValueError: Invalid Region: Region should be in 2560x1440

And the outer window frame is larger than the working area, so it is easy to go beyond it when using a high DPI