feat(sensing-server): ADR-140 semantic state record + Ruflo agent bridge (#844)

- semantic/record.rs: SemanticStateRecord (kind/room/node/timestamp/expiry/
  confidence/model_version/calibration_version/privacy_action/evidence_refs) —
  the auditable wire form of an ADR-139 SemanticState node, enriched from the
  existing SemanticEvent via RecordContext
- PrivacyAction enum (Allow/AnonymizeByRoom/StripBiometrics); StripBiometrics
  removes HR/BR evidence tags at the record boundary
- Ruflo agent bridge: MultiSignalRule.evaluate() fires AgentRoute only on
  multi-signal agreement (fall_risk + elderly_anomaly → caregiver_escalation);
  route_all() sorts by severity + dedups
- 4 tests; workspace 0 errors

Co-Authored-By: claude-flow <ruv@ruv.net>