Shaheen Gandhi fafc5e3563 Add call state notification mechanism for JSON-RPC clients
Implement CallEventListener callback pattern that fires on every call
state transition (RINGING_INCOMING, RINGING_OUTGOING, CONNECTING,
CONNECTED, ENDED). The JSON-RPC layer auto-subscribes and pushes
callEvent notifications alongside receive notifications.

Changes:
- Manager.java: Add CallEventListener interface and methods
- ManagerImpl.java: Implement add/removeCallEventListener with cleanup
- DbusManagerImpl.java: Add stub implementation (not supported over DBus)
- JsonCallEvent.java: JSON notification record for call events
- SignalJsonRpcDispatcherHandler.java: Auto-subscribe call event listeners

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
2026-03-05 16:16:07 -08:00
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