docs: Add CLAUDE.md for Claude Code guidance

Add comprehensive guidance document for Claude Code, including:
- Build and development commands using Fastlane
- Architecture overview with component diagrams
- Platform support matrix (iOS, macOS, tvOS, watchOS, visionOS)
- Testing guidelines and procedures
- Documentation system details

This document helps Claude Code understand project structure,
build system, and development practices for more effective assistance.

CLAUDE.md

@@ -0,0 +1 @@
+AGENTS.md