feat: add AGENTS.md for all packages and apps (9 files)

apps/web-tanstack/AGENTS.md

@@ -0,0 +1,15 @@
+# apps/web-tanstack — TanStack Start Reference App
+
+TanStack Start app consuming `@repo/api-client` for data and `@repo/ui` for components.
+
+## Key Files
+
+- `src/routes/__root.tsx` — Root layout with `<ApiProvider>`
+- `src/routes/index.tsx` — Home page
+
+## Rules
+
+- Use `@repo/api-client` hooks for all data fetching
+- Use `@repo/ui` components for all UI
+- File-based routing via TanStack Router (`src/routes/`)
+- Payload instance initialization goes in `src/lib/payload.ts`