Breaking changes:

- `with_relationship_hook()` renamed to `with_post_hook()`

Migration from 0.4.x:

  // Before
  SessionTracker::new(stream).with_relationship_hook(|entry, state| { ... })

  // After
  SessionTracker::new(stream).with_post_hook(|entry, state| { ... })

New features:

- `with_pre_hook()`: runs BEFORE built-in extraction, for overrides
- `with_post_hook()`: runs AFTER built-in processing (same as old hook)
- SessionState/SessionSnapshot new fields:
  - caller_id_name: from Caller-Caller-ID-Name CHANNEL_DATA
  - hangup_cause: from ChannelLifecycle Hangup detail
  - answered_at: timestamp when "has been answered" seen