feat(rpc): add target policy, protocol schemas, and tagged errors

- Add normalizeLoopbackTarget() with loopback-only URL validation
- Add JSON-RPC response decoder with schema validation
- Define 8 tagged errors using Data.TaggedError
- 20 tests covering target policy and protocol decoding
- Re-export all public types from index.ts

web/packages/rpc/tsconfig.json

@@ -5,6 +5,8 @@
     "moduleResolution": "NodeNext",
     "composite": true,
     "declaration": true,
+    "lib": ["ES2023"],
+    "types": ["node"],
     "rootDir": "src",
     "outDir": "dist"
   },