feat: add an embed mode that shows only the globe

?embed=1 shows the globe alone: clean view with the HUD, panels, welcome and
setup prompts hidden, and provider attribution kept. The page that frames it
sends views with postMessage; the app applies each through its own actions
and reports every step. Annotations in any link are drawn once it restores.
Only embed-mode documents may be framed; every other page keeps
X-Frame-Options DENY and frame-ancestors 'none', and
GEV_EMBED_FRAME_ANCESTORS can restrict who frames them.

style.css

@@ -12,6 +12,7 @@
 @import './src/ui/styles/bhote-koshi.css';
 @import './src/ui/styles/recent-imagery.css';
 @import './src/ui/styles/recording.css';
+@import './src/ui/styles/embed.css';
 @import './src/ui/styles/responsive.css';
 @import './src/ui/styles/command-dock.css';
 @import './src/ui/styles/command-dock-compact.css';