added more notes to contributing guide for UI (tensorzero#3526)

* added more notes to contributing guide for UI

* Fix formatting for steps in CONTRIBUTING.md

* Update TENSORZERO_EVALUATIONS_PATH in CONTRIBUTING.md

---------

Co-authored-by: Gabriel Bianconi <[email protected]>

Author: virajmehta

CONTRIBUTING.md

@@ -194,22 +194,24 @@ To set it up, follow these steps from the `ui` directory:
 1. Install dependencies: `pnpm install`
 2. Build the internal N-API client for TensorZero using `pnpm -r build`. If you have changed your Rust code, you may also have to run `pnpm build-bindings` from `../internal/tensorzero-node`.
 3. Create a `fixtures/.env` following the `fixtures/.env.example`.
-4. Set the following environment variables:
+4. Run `cargo build`.
+5. Set the following environment variables in your cwd `ui/` (note the previous step edited the vars in `fixtures/`):
    ```bash
    TENSORZERO_GATEWAY_URL="http://localhost:3000"
    TENSORZERO_CLICKHOUSE_URL="http://chuser:chpassword@localhost:8123/tensorzero_ui_fixtures"
    TENSORZERO_UI_CONFIG_PATH="fixtures/config/tensorzero.toml"
-   
+   TENSORZERO_EVALUATIONS_PATH="../target/debug/evaluations"
+
    # Optional: add provider credentials for optimization workflows
    OPENAI_API_KEY="..."
    FIREWORKS_API_KEY="..."
    FIREWORKS_ACCOUNT_ID="..."
    ```
-5. Launch the dependencies: `docker compose -f fixtures/docker-compose.yml up --build --force-recreate`.
+6. Launch the dependencies: `docker compose -f fixtures/docker-compose.yml up --build --force-recreate`.
 You can omit these last 2 flags to skip the build step, but they ensure you're using the latest gateway.
-6. Launch the development server: `pnpm dev`
+7. Launch the development server: `pnpm dev`
 
-Separately, you can run headless tests with `pnpm test` and Playwright tests with `pnpm test-e2e`.
+Separately, you can run headless tests with `pnpm test` and Playwright tests with `pnpm test-e2e` (the latter will require a `pnpm exec playwright install`).
 We also maintain a Docker Compose for e2e tests `fixtures/docker-compose.e2e.yml` that is used in CI for the Playwright tests.
 This file uses a different configuration that mandates credentials for image fetching.