Refactor of diffuser to use the platform infrastructure (BaseDomain, BaseNodeAdapter,
ChildRouter, commandRegistry, statusBadge). Extracts concerns into
focused modules per .claude/refactor/MODULE_SPLIT.md generic template.
Tests stay green; CONTRACT.md generated; legacy aliases preserved.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
