Sessions - changes view improvements

[lszomoru]

No description provided.

[Copilot]

Pull request overview

Improves the Agent Sessions “Changes” view (vs/sessions) by refining reactive git/repository tracking and by wiring additional context keys intended to drive toolbar/menu enablement/visibility.

Changes:

• Refactors active-session repository tracking to resolve IGitRepository via ObservablePromise rather than nested observableFromPromise values.
• Adds/binds new context keys for merge-base branch protection and “has open pull request” state, and simplifies several existing context-key bindings.
• Updates “Last turn” diff computation to use an ObservablePromise-backed observable.

Comments suppressed due to low confidence (1)

src/vs/sessions/contrib/changes/browser/changesView.ts:640

• lastTurnChangesObs uses ObservablePromise(...).resolvedValue, which throws when the underlying diffBetweenWithStats promise rejects (e.g. for a root commit where ${headCommit}^ is invalid). That exception will bubble through combinedEntriesObs and can break rendering instead of just showing an empty last-turn list. Consider using ObservablePromise(...).promiseResult and mapping errors to an empty array/undefined (optionally logging), or otherwise catching promise rejection so UI stays functional.

			if (!repository || !headCommit) {
				return constObservable(undefined);
			}

			return new ObservablePromise(repository.diffBetweenWithStats(`${headCommit}^`, headCommit)).resolvedValue;