Copilot CLI: refactor how uncommitted changes are determined before creating a new CLI session

[DonJayamanne]

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[Copilot]

Pull request overview

Refactors the Copilot CLI “uncommitted changes” detection/prompting path that runs before creating a new CLI session/worktree, and adjusts related workspace-change tracking and tests.

Changes:

• Update FolderRepositoryManager to determine uncommitted changes via gitService.getRepository(...) using the selected repository URI (and requested branch), and always use the vscode_get_modified_files_confirmation tool for the prompt.
• Remove filesystem-watcher-based cache invalidation from ChatSessionWorkspaceFolderService and simplify constructor dependencies.
• Update unit tests/fakes to align with the new repository lookup and revised service constructor.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/extension/chatSessions/vscode-node/folderRepositoryManagerImpl.ts	Refactors uncommitted-change prompting flow and repo lookup; removes old fallback confirmation path.
src/extension/chatSessions/vscode-node/chatSessionWorkspaceFolderServiceImpl.ts	Removes workspace file watcher invalidation; relies on repo HEAD change to clear cached workspace changes.
src/extension/chatSessions/vscode-node/test/folderRepositoryManager.spec.ts	Updates fake git service behavior to support new repo lookup during prompting.
src/extension/chatSessions/vscode-node/test/copilotCLIChatSessionParticipant.spec.ts	Adjusts delegate-path setup to ensure repo is discoverable via getRepository.
src/extension/chatSessions/vscode-node/test/chatSessionWorkspaceFolderService.spec.ts	Updates constructor usage and removes watcher-based cache invalidation tests.

Comments suppressed due to low confidence (1)

src/extension/chatSessions/vscode-node/folderRepositoryManagerImpl.ts:452

• Skipping the uncommitted-changes confirmation when repository.headBranchName !== branch can suppress the prompt even when there are local changes, which means the user won't get a chance to copy/move them into the new worktree. Uncommitted changes (and the file list) can still be determined regardless of the target branch; if the concern is applying them onto a different branch, consider still prompting but adding a warning about potential conflicts, or compute the list against the correct ref instead of returning undefined here.

		if (branch && repository.headBranchName !== branch) {
			return undefined;