Remove the Snow visual preset

Snow is no longer offered anywhere a style can be chosen: the Visual
Presets tray, keyboard shortcut 7, the Cockpit vision carousel, and the
set_visual_style voice action. The shader and its labels go with it;
weather snowfall and the SNOW weather condition are unaffected.

Share links keep working. Snow's enum code (6) stays reserved, so a
compact or long-form link that names it opens on Normal and drops the
Snow shader parameters without reporting them as unknown. A Scene
Director shot saved with Snow plays on Normal too. Snow's frozen share
defaults matched Normal's apart from those parameters, so no other
setting in an old link changes meaning.

The legacy voice-schema pins restore Snow before hashing, so the
unchanged pins still prove nothing else moved; the complete Realtime
payload digest is re-derived.

README.md

@@ -61,7 +61,7 @@ Start with the included data sources, then add your own. Each layer is a separat
 - **🎯 Click-to-track anything:** Camera locks on, draws a fading trail, surfaces full metadata — and a tracked fire or vessel hands you off to the nearest live camera in one click.
 - **🖊️ Voice whiteboard:** Speak annotations onto the world — real boundary polygons, marks, and routes.
 - **🛫 3D hangar:** Real per-class aircraft models — 787, ATR-72, Citation, Bell 206, MQ-9 — and a tracked contact swaps from glyph to 3D model as you close in.
-- **🎨 Reskin reality:** GLSL sensor looks over the normal globe — CRT, NVG, FLIR/thermal, Noir, Snow.
+- **🎨 Reskin reality:** GLSL sensor looks over the normal globe — CRT, NVG, FLIR/thermal, Noir.
 - **🟩 Detection overlay:** Screen-space bounding boxes and IDs on everything in view.
 - **🎖️ Military HUD:** Tactical heads-up display with intelligence-style telemetry.
 - **🌐 Global Context:** Stage the full situational picture with one switch — and get your exact view back when you leave.