- Replace RoutePeerKind with ChatType throughout codebase
- Change 'dm' literal values to 'direct' in routing/session keys
- Keep backward compat: normalizeChatType accepts 'dm' -> 'direct'
- Add ChatType export to plugin-sdk, deprecate RoutePeerKind
- Update session key parsing to accept both 'dm' and 'direct' markers
- Update all channel monitors and extensions to use ChatType
BREAKING CHANGE: Session keys now use 'direct' instead of 'dm'.
Existing 'dm' keys still work via backward compat layer.
20ae9470ea