Pure-Dart mirror of the Python crdt-sync package, module-for-module and
test-for-test, so the merge algorithm canonically agrees on both sides of
a sync between a Dart client and a Python one. No Flutter SDK dependency
(package:http only) per Workstream D's scoping decision (2026-07-04).
59 tests, clean dart analyze.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017McuA1nAi6jBT1EaS5BrVf
