Chat - more working set cleanup and refactoring

[lszomoru]

No description provided.

[Copilot]

Pull request overview

This PR refactors the chat working set rendering code to simplify parameter passing and improve code maintainability by consolidating data transformations upstream.

Changes:

• Removed unused IChatSessionFileChange import
• Simplified renderChatEditingSessionWithEntries method signature by removing intermediate observables and relying on pre-transformed IChatCollapsibleListItem observables
• Refactored statistics calculation to use unified IChatCollapsibleListItem structure instead of raw data sources, improving consistency and reducing duplication

[Copilot]

The diff stats calculation logic is duplicated between the two branches. The code should accumulate stats from both entries and sessionEntries arrays instead of using an if-else. Based on line 2588 where both arrays are combined, both arrays can contain relevant data simultaneously. Change the logic to iterate over both arrays unconditionally to avoid missing diff stats when both arrays have data.

Suggested change

	if (entries.length > 0) {
	for (const entry of entries) {
	if (entry.kind === 'reference' && entry.options?.diffMeta) {
	added += entry.options.diffMeta.added;
	removed += entry.options.diffMeta.removed;
	}
	}
	} else {
	for (const entry of sessionEntries) {
	if (entry.kind === 'reference' && entry.options?.diffMeta) {
	added += entry.options.diffMeta.added;
	removed += entry.options.diffMeta.removed;
	}
	for (const entry of entries) {
	if (entry.kind === 'reference' && entry.options?.diffMeta) {
	added += entry.options.diffMeta.added;
	removed += entry.options.diffMeta.removed;
	}
	}
	for (const entry of sessionEntries) {
	if (entry.kind === 'reference' && entry.options?.diffMeta) {
	added += entry.options.diffMeta.added;
	removed += entry.options.diffMeta.removed;