Fix theme support and improve tooling

- Fix ITheme property: selection -> selectionBackground (ghostty-web compat)
- Add dynamic body background color matching theme
- Add THEME_BACKGROUNDS mapping in local_server.py
- Add tsconfig.json for TypeScript type checking
- Update Makefile to use bun run for all frontend commands
- Add typecheck script to package.json (make build now typechecks)
- Add detailed console tracing for theme debugging
- Store fontFamily/fontSize in WebTerminal class for cell measurement

v0.6.5

tsconfig.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "noEmit": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "allowSyntheticDefaultImports": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "lib": ["ES2022", "DOM", "DOM.Iterable"]
+  },
+  "include": ["src/textual_webterm/static/js/**/*.ts"],
+  "exclude": ["node_modules"]
+}