feat(core): session timeline + failure detection + summarizer + validator

[sepehr-safari]

Scope

Build the analysis layer on top of the parser/normalizer: session timeline construction, three failure detection rules, session summarizer, and message validator.

Deliverables

• packages/core/src/timeline.ts — buildSessionTimeline(events: Event[]): Session[] correlating events by transactionId (ADR-0006), with connectorId and stationId as secondary groupings
• packages/core/src/detection.ts — detectFailures(events: Event[], sessions: Session[]): Failure[] implementing 3 rules:
  1. FAILED_AUTHORIZATION — Authorize response with idTagInfo.status = "Invalid"
  2. CONNECTOR_FAULT — StatusNotification with status = "Faulted" during an active session
  3. STATION_OFFLINE_DURING_SESSION — session has StartTransaction but no StopTransaction, or connector transitions to Unavailable/Offline during an active transaction
• packages/core/src/summarizer.ts — summarizeSession(session: Session): SessionSummary producing overview stats (event count, duration, failure count, action sequence)
• packages/core/src/validator.ts — validateMessage(event: Event): ValidationResult checking OCPP 1.6 JSON message structure compliance
• Unit tests for all modules, 70%+ coverage

Acceptance Criteria

• buildSessionTimeline() correctly groups events into sessions by transactionId
• All 3 failure detection rules work on the existing fixtures (normal-session, failed-auth, connector-fault)
• summarizeSession() produces useful stats
• validateMessage() catches structural OCPP message violations
• 70%+ coverage

Dependencies

• docs: protocol scope + trace-format design spike #19 (parser + normalizer)

Branch

feat/core-timeline-detection