Vendor pyusb wheel for offline Windows source installs

Include pyusb-1.2.1-py3-none-any.whl under vendor/wheels and wire
setup scripts to pip install --no-index --find-links.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -1,4 +1,5 @@
 .venv/
+.venv-build/
 .venv-build-win/
 __pycache__/
 *.py[cod]
@@ -10,7 +11,8 @@ build/
 analysis/
 *.zip
 *.tar.gz
-# keep vendor/libusb-1.0.dll in repo for Windows bundling
-!vendor/libusb-1.0.dll
-.venv-build/
 hub.log
+# keep vendor binaries
+!vendor/libusb-1.0.dll
+!vendor/wheels/
+!vendor/wheels/*.whl