Fixes two critical bugs:
1. Unread badge not clearing when opening chat - incoming messages weren't marked as viewed
2. Only last 2-3 messages loaded instead of full history due to incorrect break condition
Changes:
- Add incoming message IDs to pending_view_messages queue on chat open
- Remove premature break in get_chat_history() that stopped after 2 messages
- Add FakeTdClient.pending_view_messages field for testing
- Implement process_pending_view_messages() in FakeTdClient
Tests added:
- test_incoming_message_shows_unread_badge: verify "(1)" appears for unread
- test_opening_chat_clears_unread_badge: verify badge clears after opening
- test_opening_chat_loads_many_messages: verify all 50 messages load, not just last few
All 28 chat_list tests pass.
dec60ea74e