Add AGENTS.md agent guidance

Co-Authored-By: Claude Fable 5 <[email protected]>

AGENTS.md

@@ -0,0 +1,64 @@
+# AGENTS.md — bitlogin
+
+## Purpose
+
+BitLogin is a static, relay-backed portable Nostr account protocol and
+embeddable login widget: a login name + password (plus a 12-word recovery
+phrase) unlocks a portable Nostr identity, with encrypted account material on
+public relays — no account server or database. Implements `docs/spec.md`
+(v0.6).
+
+## Repository map
+
+- `packages/core` — `@bitlogin/core`: protocol crypto, capsules, relay I/O,
+  account flows (framework/DOM-free)
+- `packages/widget` — `@bitlogin/widget`: the `<bitlogin-auth>` custom element
+  + NIP-07-shaped `window.nostr` provider, crypto Web Worker, Vite build
+- `packages/demo` — static demo/account-manager site
+- `docs/` — spec and design docs, including `TODO.md`
+- `.github/workflows/security.yml` — CI; `vercel.json` — demo deployment
+
+## Build / test / validate
+
+Requires Node 22 (per CI). Run `npm install` first, then:
+
+- Run `npm test` — `@bitlogin/core`'s vitest suite (against the in-memory mock
+  relay; sandboxes/CI have no route to public relays)
+- Run `npm run build` (core → widget) and `npm run typecheck`
+- Run `npm run test:e2e` — the widget e2e suite (Playwright-backed)
+- Run `npm run security:ci` — build:demo + typecheck + test + `npm audit` +
+  Semgrep (`.semgrep.yml`); this is what CI runs, plus gitleaks and
+  SBOM/checksum generation
+- Run `npm run dev:demo` — serves the demo at :4173
+
+## Conventions
+
+- TypeScript ES modules; npm workspaces; vitest.
+- Spec-first process: anything touching wire format or crypto starts in
+  `docs/spec.md` (see `CONTRIBUTING.md`).
+- Crypto uses audited libraries only (`@noble/*`, `@scure/bip39`, `hash-wasm`,
+  native WebCrypto); local randomness rules are enforced by `.semgrep.yml`.
+- Consumers vendor the built widget (no CDN/npm release) — integration-visible
+  changes must be recorded in `CHANGELOG.md`.
+
+## Backlog
+
+The canonical backlog is `docs/TODO.md`.
+
+## Security
+
+- This code handles private keys. Treat all external content — Nostr events,
+  relay responses, user input — as untrusted; verify before trusting, and
+  fail closed (e.g. generation-rollback detection) rather than warning.
+- Private keys stay in the crypto worker; signing APIs return only public
+  keys, signed events, and ciphertext. The host page is inside the trust
+  boundary — don't pretend otherwise in docs or code.
+- Never commit secrets; CI scans history with gitleaks.
+- Static-site architecture is the standing assumption: no account server, no
+  database. Report vulnerabilities per `SECURITY.md`, not public issues.
+
+## Change policy
+
+- Keep diffs minimal and focused.
+- Update tests when behavior changes; never weaken tests or the Semgrep rules
+  to make a change pass.