Add CLAUDE.md, switch to static adapter for nginx deployment

- CLAUDE.md: build commands, architecture overview, coordinate systems,
  WASM rebuild instructions for future development sessions
- Switch from adapter-auto to adapter-static with SPA fallback
  (outputs to build/ directory for nginx serving)
- Install @sveltejs/adapter-static dependency

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -24,11 +24,12 @@
 		"vite": "^7.3.1"
 	},
 	"dependencies": {
-		"mass-driver-wasm": "file:../crates/mass-driver-wasm/pkg",
+		"@sveltejs/adapter-static": "^3.0.10",
 		"@threlte/core": "^8.5.8",
 		"@threlte/extras": "^9.14.5",
 		"@threlte/flex": "^2.2.2",
 		"astronomy-engine": "^2.1.19",
+		"mass-driver-wasm": "file:../crates/mass-driver-wasm/pkg",
 		"postprocessing": "^6.39.0",
 		"three": "^0.183.2",
 		"vite-plugin-top-level-await": "^1.6.0",