feat: add proto codegen pipeline with buf and connect-es

- Add llm-multiverse repo as git submodule for proto files
- Configure buf with @bufbuild/protoc-gen-es for TypeScript codegen
- Generate typed Connect service stubs to src/lib/proto/
- Add `generate` npm script for proto regeneration
- Exclude generated proto files from ESLint

Closes #2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

buf.gen.yaml

@@ -0,0 +1,8 @@
+version: v2
+plugins:
+  - local: protoc-gen-es
+    out: src/lib/proto
+    opt:
+      - target=ts
+inputs:
+  - directory: proto/upstream/proto