v0.4.0 — API parity pass

API-parity pass. Brings the Swift SDK's surface into alignment with the
Flutter and Kotlin siblings so callers see the same shape across all
three platforms.

Breaking

• BehaviorEvent: rename type → eventType and payload → metrics
  to match the canonical wire format (event_type / metrics).
• SynheartBehavior.startSession() now returns a BehaviorSession
  object with .sessionId, .startTimestamp, .end() throws, and
  .getCurrentDuration(). Callers that read the session ID can use
  try sdk.startSession().sessionId.
• Minimum iOS deployment target bumped from 12.0 to 13.0 (required for
  AsyncStream and async/await). .ephemeral notification
  authorization is gated behind #available(iOS 14.0, *).

Added

• events: AsyncStream<BehaviorEvent> — async-iteration API mirroring
  the Kotlin onEvent: Flow and Flutter onEvent: Stream. Coexists
  with the existing setEventHandler callback via internal fan-out.
• checkNotificationPermission() async -> Bool and
  requestNotificationPermission() async -> Bool via
  UNUserNotificationCenter. iOS-no-op checkCallPermission /
  requestCallPermission for signature parity with Flutter/Kotlin.
• BehaviorSession wrapper class.
• Nested types on BehaviorSessionSummary matching Kotlin/Flutter:
  MotionState, DeviceContext, ActivitySummary, DeepFocusBlock,
  BehavioralMetricsStruct, NotificationSummary, SystemState,
  TypingMetrics, TypingSessionSummary. ML-scored and aggregate
  fields default to nil/zeros until a downstream consumer populates
  them.

Tests

• All 33 SDK tests pass on the renamed surface.

Full Changelog: https://github.com/synheart-ai/synheart-behavior-swift/commits/v0.4.0