Copilot CLI - publish statistics for session using git worktree

[lszomoru]

No description provided.

[Copilot]

Pull Request Overview

This PR adds a new diffWithHEADShortStats method to the git service for retrieving git diff statistics (files changed, insertions, deletions) including untracked files. The method is used in the Copilot CLI chat sessions feature to display statistics for worktree sessions.

• Adds diffWithHEADShortStats method to git service interface and implementations
• Implements custom logic to include untracked files in statistics by counting their lines
• Updates Copilot CLI chat session items to display diff statistics and refactors tooltip/description generation

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/platform/git/common/gitService.ts	Adds interface definition for diffWithHEADShortStats method
src/platform/git/vscode/git.d.ts	Adds type definition for repository diffWithHEADShortStats method
src/platform/git/vscode/gitServiceImpl.ts	Implements diffWithHEADShortStats with custom handling for untracked files
src/platform/test/node/simulationWorkspaceServices.ts	Adds stub implementation to testing git service
src/extension/prompt/node/test/repoInfoTelemetry.spec.ts	Adds mock method to test git service
src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts	Uses new method to display statistics for CLI sessions and refactors session item generation

[DonJayamanne]

Question about work tree & Promise.all