Add updating draft state to update_pull_request tool

[mattdholloway]

Closes: #501 and #423

This is a copy of the comment in issue 501:

I've had a look at implementing this as an extension of the update_pull_request tool (using GraphQL). I've chosen to use a new draft parameter as a boolean for this for a few reasons:

• In the GraphQL spec for pull requests, 'draft' is separate to 'state' as a PR can be both closed as a draft, open as ready for review, etc (ref:

"""
The possible states of a pull request.
"""
enum PullRequestState {
  """
  A pull request that has been closed without being merged.
  """
  CLOSED

  """
  A pull request that has been closed by being merged.
  """
  MERGED

  """
  A pull request that is still open.
  """
  OPEN
}

  Identifies if the pull request is a draft.
  """
  isDraft: Boolean!

  """

• Setting if the PR is a draft using GraphQL requires a separate implementation to the current existing REST calls, and I felt it would introduce unneeded complexity having a totally separate code path based on an enum variant

[Copilot]

Pull Request Overview

This PR adds draft state management functionality to the update_pull_request tool, allowing users to mark pull requests as drafts or ready for review through GraphQL mutations.

• Adds a new draft boolean parameter to the update_pull_request tool
• Implements GraphQL-based draft state mutations (convertPullRequestToDraft and markPullRequestReadyForReview)
• Updates the tool to handle both REST API updates for traditional fields and GraphQL mutations for draft state changes

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/github/tools.go	Updates function signature to include GraphQL client parameter
pkg/github/pullrequests.go	Adds draft parameter handling and GraphQL mutation logic for draft state changes
pkg/github/pullrequests_test.go	Adds comprehensive test coverage for draft functionality with mock GraphQL clients
pkg/github/toolsnaps/update_pull_request.snap	Updates tool schema snapshot to include new draft parameter
README.md	Documents the new draft parameter in the tool usage section

Comments suppressed due to low confidence (1)

pkg/github/pullrequests.go:456

• The comment is misleading - it says 'Current state is draft' but the value is false, indicating it's not a draft. The comment should be corrected to reflect the actual state.

				mcp.Enum("asc", "desc"),

[Copilot]

The REST client is retrieved twice in this function (lines 311 and 400). Consider retrieving it once at the beginning and reusing it to improve efficiency and reduce duplication.

Suggested change

	}
	// Reuse the client retrieved earlier