Add AI mockups for the seven remaining catalogue screens

The design catalogue grew to 19 screens, but only the original twelve had an AI
reference; the rest still showed "design -" in `list`. Generated the missing set
so every screen can be reviewed against an intended look:

- wand screening (metal-detected panel with carried items and allow/deny)
- Joke Shop queue, TV Studio arrival, crowd panic, responder arrival
- body-camera timeline, escalation HUD

`generate` now loads `.env` the same way `judge` does, so `--ai` no longer needs
the API key exported by hand. Each reference is 1280x720; the twelve existing
mockups were kept (no `--force`).

Verification: `list` reports 19 designs, Python tooling 53/53, headless suite
182/182, `compare` still 6 good / 0 bad on the captured screens. Version 0.3.2.

tools/screen_designs.py

@@ -592,6 +592,7 @@ def _generate_ai(screen, model, request_size):
 
 
 def generate(args):
+    _load_env_file()
     DESIGNS_DIR.mkdir(parents=True, exist_ok=True)
     failed = []
     selected = [screen for screen in SCREENS