feat: add CLAUDE.md with extension dev and ecosystem context

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: vveerrgg

CLAUDE.md

@@ -0,0 +1,61 @@
+# CLAUDE.md — nostrkey.browser.plugin.src
+
+## What This Is
+NostrKey browser extension — cross-browser Nostr key management, encrypted vault, and identity layer. The core codebase that also powers the iOS and Android apps.
+
+## Ecosystem Position
+NostrKey is **the hand that holds the baseball card**. It manages your private keys, signs events, encrypts data, and connects you to your NostrKeep relay and npub.bio identity. Free, open source (MIT), forked from ursuscamp/nostore.
+
+## Current Version
+v1.5.5 — Live on Chrome Web Store, Android (Google Play), iOS (App Store submission in progress)
+
+## Tech Stack
+- Vanilla JS (Alpine.js was removed)
+- esbuild bundler
+- Tailwind CSS
+- nostr-crypto-utils for protocol operations
+- Chrome Manifest V3
+
+## Build Commands
+```bash
+npm install
+npm run build           # Safari: Tailwind + esbuild
+npm run build:chrome    # Chrome → distros/chrome/
+npm run build:all       # Both targets
+npm run build:all:prod  # Both, minified
+npm run watch           # Watch mode (JS, Safari)
+npm run watch-tailwind  # Watch mode (CSS)
+```
+
+## Chrome Dev
+1. `npm run build:chrome`
+2. `chrome://extensions/` → Developer mode → Load unpacked → `distros/chrome/`
+
+## NIPs Implemented
+NIP-01, NIP-04 (deprecated), NIP-07, NIP-19, NIP-44, NIP-46, NIP-49, NIP-78
+
+## Key Features
+- NIP-07 `window.nostr` signing
+- NIP-46 nsecBunker (remote signing)
+- NIP-44 encryption (ChaCha20-Poly1305)
+- Encrypted .md vault + API key vault (NIP-78)
+- Multi-profile with per-site permissions
+- Master password with auto-lock
+- Cross-device sync via storage.sync
+- WCAG AA accessibility
+
+## Architecture
+Extension uses background service worker + sidepanel UI. Mobile apps (iOS/Android) wrap this in dual-WebView architecture with native bridges (IOSBridge.swift / AndroidBridge.kt).
+
+## Conventions
+- Vanilla JS, no frameworks
+- kebab-case file names
+- Chrome Web Store zips go in `distros/` folder
+- WCAG AA contrast, aria-labels, reduced-motion support
+
+## Related Repos
+- `nostrkey.app.ios.src` — iOS app (WKWebView wrapper, v1.1.1)
+- `nostrkey.app.android.src` — Android app (WebView wrapper, v1.1.1)
+- `nostrkey.bizdocs.src` — business strategy docs
+- `npub-bio-landingpage` — npub.bio (uses NostrKey for NIP-07 connect)
+- `nostrkeep.srvr.relay.src` — NostrKeep relay (NostrKey points keys here)