[skip ci] Add AGENTS.md

AGENTS.md

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+# AGENTS.md — Atalaya
+
+## Architecture
+
+npm workspace: Cloudflare Worker (`src/`) + Astro 6 SSR app (`status-page/`).
+
+- **Worker entrypoint**: `src/index.ts` — `fetch` + `scheduled` handlers, `RegionalChecker` Durable Object
+- **Astro entrypoint**: `status-page/src/pages/index.astro` — single-page SSR app
+- **Static assets**: `status-page/dist/client/` served via `ASSETS` binding (`run_worker_first = true`)
+- **Shared types**: `src/types.ts` imported via `@worker/types` alias in `status-page/tsconfig.json`
+- **Auth**: `status-page/src/lib/auth.ts`, configured via `STATUS_PUBLIC`, `STATUS_USERNAME`, `STATUS_PASSWORD` env vars
+
+## Commands
+
+### Root (Worker)
+
+```bash
+npm run dev                   # wrangler dev
+npm run test                  # vitest (17 test files)
+npm run typecheck             # tsc --noEmit
+npm run check                 # typecheck + lint + format:check
+npm run check:fix             # auto-fix lint + format
+npm run deploy                # build:pages + wrangler deploy
+vitest run src/path/to.test.ts  # single test (no npx needed)
+```
+
+### Pages workspace
+
+```bash
+npm run dev:pages             # astro dev
+npm run build:pages           # astro build → status-page/dist/
+npm run test:pages            # vitest run (auth tests)
+npm run check:pages           # astro check + tsc --noEmit
+npm run lint:pages            # eslint (astro plugin)
+```
+
+### Verification order
+
+Before commit: `npm run check && npm run test && npm run build:pages && npm run check:pages`
+
+`npm run check` = typecheck + Oxlint (worker) + ESLint (dedup via `eslint-plugin-oxlint`). Pages uses `eslint-plugin-astro`.
+
+## Gotchas
+
+- **`.js` extensions in imports**: All worker imports use `.js` extensions (`import { foo } from './bar.js'`). Required for ESM resolution with `moduleResolution: "bundler"`.
+- **D1 requires bind parameters**: Use `WHERE 1=?` with `.bind(1)` for queries that would otherwise have no parameters.
+- **Database naming**: D1 columns are `snake_case`, TypeScript properties are `camelCase`. Map at query boundary.
+- **`--legacy-peer-deps`**: Needed when installing Pages dependencies (`@astrojs/check` declares `typescript@^5` but project uses TypeScript 6).
+- **Pages `dist/` and `.astro/`**: Build artifacts, gitignored.
+- **Astro SSR build artifact**: Worker dynamically imports `../status-page/dist/server/index.mjs` at runtime — uses `@ts-expect-error`.
+- **Astro 6 + @astrojs/cloudflare v13 workarounds**: `status-page/astro.config.mjs` includes `fixBuildRollupInput` plugin and `prerenderEnvironment: 'node'`.
+- **Monitor config in `wrangler.toml`**: `MONITORS_CONFIG` env var contains full YAML config inline. Secrets interpolated via `${ENV_VAR}` syntax (`src/utils/interpolate.ts`).
+
+## Code Style
+
+- **Formatting**: Prettier — single quotes, semicolons, 100 char width, trailing commas ES5.
+- **Linting**: Oxlint (worker) + ESLint with `eslint-plugin-oxlint` dedup. Pages uses `eslint-plugin-astro`.
+- **Types**: `type` for aliases, `interface` for object shapes. Explicit return types.
+- **Naming**: files `kebab-case.ts`, types `PascalCase`, variables `camelCase`, DB fields `snake_case`.
+- **Tests**: `*.test.ts` colocated with source. Vitest with `vi` for mocks.