Fix review findings and Windows setup issues found in testing

- Run the server with -X utf8: the bundled Windows Python ignores PYTHON* variables.
- Quote every argument in Windows terminal commands, so cmd metacharacters are literal.
- frame_connect: accept HOST:PORT, validate input, retry the config swap while
  Windows' ssh.exe holds ~/.ssh/config locked, and don't apply 0o700 on Windows.
- Never use rsync on Windows; unbounded stream queue; validate FRAME_ALIAS;
  more Linux terminals; bundle the window icon; docs and wording fixes.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/frame-control.md

@@ -8,11 +8,11 @@ As of 2026-09-25 no other desktop app manages the Frame end to end.
 the headset over SSH. [FrameDrop](https://framedropvr.com) sideloads but is
 Windows-only. Steam Link views the headset.
 
-You can also run the same UI in a browser without the app, from a checkout on
-macOS or Linux:
+You can also run the same UI in a browser without the app, from a checkout:
 
 ```sh
-./scripts/frame-ui.sh        # opens http://127.0.0.1:47810 in its own window
+./scripts/frame-ui.sh        # macOS: opens http://127.0.0.1:47810 in its own window
+python3 ui/server.py         # anywhere: then open http://127.0.0.1:47810
 ```
 
 ## Features