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>

implementation-plans/_index.md

@@ -3,3 +3,4 @@
 | Issue | Title                                                  | Status       | Plan                         |
 | ----- | ------------------------------------------------------ | ------------ | ---------------------------- |
 | #1    | Project scaffolding: SvelteKit + Tailwind + TypeScript | COMPLETED    | [issue-001.md](issue-001.md) |
+| #2    | Proto codegen pipeline for TypeScript gRPC-Web stubs   | IMPLEMENTING | [issue-002.md](issue-002.md) |

implementation-plans/issue-002.md

@@ -0,0 +1,49 @@
+---
+---
+
+# Issue #2: Proto codegen pipeline for TypeScript gRPC-Web stubs
+
+**Status:** IMPLEMENTING
+**Issue:** https://git.shahondin1624.de/llm-multiverse/llm-multiverse-ui/issues/2
+**Branch:** `feature/issue-2-proto-codegen`
+
+## Summary
+
+Set up buf + @connectrpc/connect-web to generate TypeScript client stubs from the llm-multiverse proto files. Use a git submodule to consume proto files. Output generated code to `src/lib/proto/`.
+
+## Acceptance Criteria
+
+- [ ] Codegen toolchain chosen and configured (buf + connect-es)
+- [ ] Proto files from llm-multiverse repo consumed (git submodule)
+- [ ] TypeScript gRPC-Web client stubs generated to `src/lib/proto/`
+- [ ] `generate` npm script added to package.json
+- [ ] Generated types are importable and type-safe
+
+## Implementation Phases
+
+### Phase 1: Add proto files via git submodule
+
+Add the `llm-multiverse` repo as a git submodule at `proto/upstream` to keep proto files in sync.
+
+### Phase 2: Configure buf for connect-es codegen
+
+Install buf CLI dependencies and configure:
+- `@bufbuild/protobuf` — runtime protobuf library
+- `@connectrpc/connect` — Connect protocol runtime
+- `@connectrpc/connect-web` — browser transport
+- `@bufbuild/protoc-gen-es` — protobuf ES codegen plugin
+- `@connectrpc/protoc-gen-connect-es` — Connect service codegen plugin
+
+Create `buf.gen.yaml` in project root targeting `src/lib/proto/` output.
+
+### Phase 3: Generate stubs and verify
+
+Run `npx buf generate` and verify generated TypeScript files are importable and type-safe.
+
+### Phase 4: Add npm script
+
+Add `"generate": "buf generate proto/upstream/proto"` to package.json.
+
+## Deviations
+
+(none yet)