fix(core): prevent divergence with null map values

[zxch3n]

• diff: treat null as a present value when detecting added keys; guard container insertions with actual value type; fall back to value-based inference when schema/
  type mismatches occur and warn to avoid divergence.
• mirror: gate consistency check by checkStateConsistency (not debug); include raw doc.toJSON() in divergence log for easier debugging.
• state: add checkStateConsistency option to createStore and plumb through to Mirror.
• test(core): add null-in-map consistency tests and stabilize existing state tests with explicit commits.
• chore(deps): bump loro-crdt to ^1.7.0 across core/react/jotai and update lockfile.