feat: reaction events in watch + react command

[pangu25]

Summary

This PR addresses issues #24 and #26 by adding:

1. --reactions flag for watch command (Feature request: Include reactions/tapbacks in message output #26)

   • Include tapback/reaction events in the stream
   • Events include metadata: is_reaction, reaction_type, reaction_emoji, is_reaction_add, reacted_to_guid

2. imsg react command (Feature request: Send tapback reactions #24)

   • Send tapback reactions via UI automation (System Events)
   • Supports standard tapbacks: love, like, dislike, laugh, emphasis, question
   • Supports custom emoji reactions (iOS 17+/macOS 14+)

Usage

Watch with reactions

# Stream messages AND reaction events
imsg watch --chat-id 1 --reactions --json

Output includes reaction events with metadata:

{
  "id": 12345,
  "chat_id": 1,
  "is_reaction": true,
  "reaction_type": "like",
  "reaction_emoji": "👍",
  "is_reaction_add": true,
  "reacted_to_guid": "ABC123-DEF456"
}

Send reactions

# Standard tapback
imsg react --chat-id 1 --reaction like

# Custom emoji
imsg react --chat-id 1 -r 🎉

Limitations

The react command:

• Only reacts to the MOST RECENT incoming message (limitation of Cmd+T shortcut)
• Requires Messages.app to be running
• Uses UI automation which requires accessibility permissions
• Works best when the chat is already open in Messages.app

Testing

Built and tested locally on macOS 15. All existing tests pass.

Closes #24
Closes #26