sessions - fix wrong use of ahead/behind in sync action

[bpasero]

No description provided.

[Copilot]

Pull request overview

Fixes the ahead/behind values used to label the Git sync action in the Agent Sessions window, and hardens repository-observer lifecycle to avoid attaching observers for stale repositories.

Changes:

• Ensure registerSyncAction receives (behind, ahead) rather than (ahead, behind).
• Introduce a per-repository DisposableStore to prevent late openRepository resolutions from wiring observers after the session/worktree has changed.

Comments suppressed due to low confidence (1)

src/vs/sessions/contrib/gitSync/browser/gitSync.contribution.ts:55

• When switching active sessions, _gitRepoDisposables.clear() disposes the previous repo autorun, but _syncActionDisposable and contextKey can remain in their previous state until the new openRepository resolves and the new autorun runs. This can leave a stale sync action/counts visible briefly (or longer if openRepository never resolves for the new worktree). Consider clearing _syncActionDisposable and setting contextKey to false before kicking off openRepository (or when repoDisposables.isDisposed is detected) so the UI doesn’t show outdated ahead/behind info.

			const repoDisposables = this._gitRepoDisposables.add(new DisposableStore());
			this.gitService.openRepository(worktreeUri).then(repository => {
				if (repoDisposables.isDisposed) {
					return;
				}