Add new XMTP channel extension for decentralized messaging:
- Direct messages (DMs) and group conversations
- Text messages, reactions, and attachments
- ENS address resolution for human-readable names
- Quantum-resistant encryption (MLS protocol)
- Multi-account support with per-account configuration
- Database isolation and network selection (dev/production)
- Comprehensive onboarding with wallet generation
Includes wallet generation scripts, example configurations,
troubleshooting guide, and test coverage for schemas, ENS
resolution, multi-account handling, and onboarding flows.
Note: Tests use Node's test runner format (node:test) and
should be converted to Vitest format in follow-up work.
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