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

[sepehr-safari]

Summary

Implements the session timeline builder, three failure detection rules, session summarizer, and OCPP message validator.

Closes #21

Changes

New files

• packages/core/src/timeline.ts — buildSessionTimeline() correlating events by transactionId (ADR-0006), with connectorId and stationId as secondary groupings
• packages/core/src/detection.ts — detectFailures() implementing 3 rules:
  1. FAILED_AUTHORIZATION — Authorize response with idTagInfo.status = "Invalid"
  2. CONNECTOR_FAULT — StatusNotification with status = "Faulted" during active session
  3. STATION_OFFLINE_DURING_SESSION — session has StartTransaction but no StopTransaction, or connector transitions to Unavailable/Offline during active transaction
• packages/core/src/summarizer.ts — summarizeSession() / summarizeSessions() producing overview stats (event count, duration, failure count, action sequence)
• packages/core/src/validator.ts — validateMessage() / validateMessages() checking OCPP 1.6 JSON message structure compliance
• 40 new unit tests (10 timeline + 11 detection + 5 summarizer + 14 validator)

Updated files

• packages/core/src/index.ts — barrel exports for all new modules
• CURRENT_STATE.md — updated to reflect v0.1.0 progress

Test Coverage

• All 3 detection rules tested against existing fixtures
• Timeline builder tested with single session, multiple sessions, empty events, missing StopTransaction
• Summarizer tested with real fixture data
• Validator tested with valid messages, invalid structure, type inconsistency, response matching

Verification

• pnpm lint — ✅
• pnpm typecheck — ✅
• pnpm test — ✅ (147 tests, all passing)
• pnpm build — ✅
• pnpm format:check — ✅