perf: strip OpenCV ffmpeg DLL and PyWin32 help from portable build

- Remove opencv_videoio_ffmpeg (28MB) — only needed for video file I/O,
  camera capture uses cv2.VideoCapture which links directly to DirectShow
- Remove PyWin32.chm help file (2.6MB)
- Keep cv2.pyd intact (needed for resize, cvtColor, camera)

Future: migrate non-camera cv2 usage to Pillow, replace winsdk (37MB
monolithic binary) with lighter notification API.

build-dist-windows.sh

@@ -291,16 +291,17 @@ rm -rf "$SITE_PACKAGES"/pip "$SITE_PACKAGES"/pip-* 2>/dev/null || true
 rm -rf "$SITE_PACKAGES"/setuptools "$SITE_PACKAGES"/setuptools-* "$SITE_PACKAGES"/pkg_resources 2>/dev/null || true
 rm -rf "$SITE_PACKAGES"/_distutils_hack 2>/dev/null || true
 
-# Remove pythonwin GUI IDE (ships with pywin32 but not needed)
+# Remove pythonwin GUI IDE and help file (ships with pywin32 but not needed)
 rm -rf "$SITE_PACKAGES"/pythonwin 2>/dev/null || true
+rm -f "$SITE_PACKAGES"/PyWin32.chm 2>/dev/null || true
 
-# OpenCV: remove unused extra modules and data (~40MB savings)
+# OpenCV: remove ffmpeg DLL (28MB, only for video file I/O, not camera),
+# Haar cascades (2.6MB), and misc dev files
 CV2_DIR="$SITE_PACKAGES/cv2"
 if [ -d "$CV2_DIR" ]; then
-    # Keep only the core .pyd and python wrapper
-    find "$CV2_DIR" -name "*.pyd" ! -name "cv2*" -delete 2>/dev/null || true
+    rm -f "$CV2_DIR"/opencv_videoio_ffmpeg*.dll 2>/dev/null || true
     rm -rf "$CV2_DIR/data" "$CV2_DIR/gapi" "$CV2_DIR/misc" "$CV2_DIR/utils" 2>/dev/null || true
-    rm -rf "$CV2_DIR/typing_stubs" 2>/dev/null || true
+    rm -rf "$CV2_DIR/typing_stubs" "$CV2_DIR/typing" 2>/dev/null || true
 fi
 
 # numpy: remove tests, f2py, typing stubs