build: add client-side TypeScript compilation pipeline

Adds scripts/build-client.mjs which uses esbuild to compile TypeScript
files in src/scripts/client/ into minified IIFE bundles, then writes
them as TypeScript string-constant modules in src/scripts/generated/.

- Adds build:client npm script; wires it as prebuild and predev hooks
- Adds src/scripts/client/tsconfig.json with DOM lib for IDE support
- Excludes src/scripts/client/ from the root Worker tsconfig to avoid
  DOM type conflicts with the Cloudflare Workers runtime types

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

tsconfig.json

@@ -17,5 +17,5 @@
     "jsxImportSource": "hono/jsx"
   },
   "include": ["src/**/*"],
-  "exclude": ["node_modules", "dist"]
+  "exclude": ["node_modules", "dist", "src/scripts/client/**/*"]
 }