Mcp UI apps with extra functionality

[mattdholloway]

Summary

This pull request introduces a new backend tool for fetching UI-related repository data and integrates it into the PR creation UI, enabling dynamic branch selection and repository search. It also includes comprehensive tests for the new tool.

Why

Expands on #1957

What changed

Backend: UI Data Fetch Tool

• Adds the new ui_get tool to provide UI data (labels, assignees, milestones, issue types, branches) for MCP Apps, including its schema and logic for fetching data using GitHub APIs. [1] [2]
• Integrates the ui_get tool into the server toolset, making it available as an insiders-only feature.
• Includes comprehensive tests for the new tool, covering various scenarios and error handling.

Frontend: Pull Request Creation UI Enhancements

• Updates the PR creation app to support repository search and selection, and dynamically loads branches for the chosen repository using the new ui_get tool. [1] [2]
• Adds UI state and logic for filtering and selecting base/head branches, preventing invalid selections (e.g., same branch for base and head). [1] [2]
• Imports additional icons and types to support new UI elements for repositories and branches. [1] [2] [3]

Summary of Most Important Changes

Backend: New Tool for UI Data

• Implements the ui_get tool, enabling MCP Apps to fetch labels, assignees, milestones, issue types, and branches for a repository, with robust error handling and schema validation. [1] [2]
• Adds tests for ui_get, ensuring correct behavior and error responses for different scenarios.
• Registers ui_get as an insiders-only tool in the server toolset.

Frontend: PR Creation UI Improvements

• Integrates repository search and selection, updating state and UI to reflect the chosen repository.
• Dynamically loads and filters branches for base/head selection, using the new backend tool and preventing invalid branch combinations. [1] [2]
• Adds relevant UI types and icons to support these enhancements. [1] [2] [3]

MCP impact

• No tool or API changes
• Tool schema or behavior changed
• New tool added

Prompts tested (tool changes only)

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)