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### Related GitHub Issue

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Closes: # <!-- Replace with the issue number, e.g., Closes: #123 -->

### Description

This PR introduces an emoji reaction feature, allowing users to add emoji reactions to any visible task messages.

Key implementation details include:
- **Schema Extension**: The `ClineMessage` type in `packages/types/src/message.ts` was extended to include a `reactions` field (mapping emoji strings to counts).
- **Frontend Component**: A new `EmojiReactions.tsx` component was created to display reactions, provide an emoji picker, and handle user interactions.
- **UI Integration**: The `ChatRow.tsx` component was updated to integrate the `EmojiReactions` component for text, completion, and user feedback message types. Reactions are only displayed for complete (non-partial) messages.
- **Backend Logic**: `Task.ts` now includes `addReaction` and `removeReaction` methods to manage reaction counts, ensuring persistence and real-time updates via `postStateToWebview`.
- **Communication Protocol**: `WebviewMessage.ts` and `webviewMessageHandler.ts` were updated to support `addReaction` and `removeReaction` message types for communication between the webview and the extension backend.

This feature provides an intuitive way for users to interact with task messages, with reactions persisting across sessions and updating in real-time.

### Test Procedure

To test this feature:
1.  Open a task in Roo Code that contains various types of messages (e.g., AI text responses, completion results, user feedback).
2.  Hover over an eligible message (non-partial text, completion, or user feedback). A small "😊" button should appear.
3.  Click the "😊" button to open the emoji picker.
4.  Click on several different emojis (e.g., 👍, ❤️, 😂) to add reactions. Verify that the emoji and its count appear next to the message.
5.  Click on an existing reaction button to remove your reaction. Verify that the count decreases or the reaction disappears if it was the last one.
6.  Add multiple reactions to the same message and verify counts update correctly.
7.  Close and reopen the task, or restart VS Code, to verify that reactions persist.
8.  Verify that reactions do not appear on message types that are not text, completion, or user feedback (e.g., tool outputs, diffs).

### Pre-Submission Checklist

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- [ ] **Issue Linked**: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
- [x] **Scope**: My changes are focused on the linked issue (one major feature/fix per PR).
- [x] **Self-Review**: I have performed a thorough self-review of my code.
- [x] **Testing**: New and/or updated tests have been added to cover my changes (if applicable).
- [x] **Documentation Impact**: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
- [x] **Contribution Guidelines**: I have read and agree to the [Contributor Guidelines](/CONTRIBUTING.md).

### Screenshots / Videos

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Please provide screenshots or a short video demonstrating the emoji reaction feature in action, showing:
-   The "😊" button appearing on hover.
-   The emoji picker opening.
-   Adding and removing reactions.
-   Reaction counts updating.

### Documentation Updates

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- [ ] Yes, documentation updates are required. (Please describe what needs to be updated or link to a PR in the docs repository).
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- [ ] No documentation updates are required.
- [x] Yes, documentation updates are required. A detailed implementation summary has been added to `emoji-reactions-implementation.md` which can be used to update user-facing documentation.

### Additional Notes

None.

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