Add Model Garden page as first tab on Models & Endpoints

- Created model_garden component with same card-grid style as guardrail garden
- Added 'What's New' section that detects new models from model_prices.json
- Uses model cost map API as single source of truth (no duplicate data)
- Grouped providers with logos, model counts, modes, and capabilities
- Provider detail view with Overview and searchable Models table
- Integrated as first tab on the Models & Endpoints page
- Fixed pre-existing merge conflict in ToolPolicies.tsx
- Updated AGENTS.md with UI dev server instructions

Co-authored-by: Ishaan Jaff <ishaan-jaff@users.noreply.github.com>

AGENTS.md

@@ -224,4 +224,12 @@ See `CLAUDE.md` and the `Makefile` for standard commands. Key notes:
 cd litellm && poetry run ruff check .
 ```
 
-Ruff is the primary fast linter. For the full lint suite (including mypy, black, circular imports), run `make lint` per `CLAUDE.md`.
+Ruff is the primary fast linter. For the full lint suite (including mypy, black, circular imports), run `make lint` per `CLAUDE.md`.
+
+### Running the UI dashboard (dev mode)
+
+```bash
+cd ui/litellm-dashboard && NEXT_PUBLIC_PROXY_BASE_URL=http://localhost:4000 npx next dev -p 3000
+```
+
+The proxy on port 4000 serves a pre-built static UI from `litellm/proxy/_experimental/out/`. For development, use the Next.js dev server on port 3000 which picks up live code changes. The `next lint` script has a pre-existing issue (tries to find a `lint` directory); `npm run build` is the reliable check for TypeScript/compilation errors. Vitest tests: `npx vitest run --pool=forks` (full suite may take several minutes; filter to specific dirs for faster feedback).