Room list: avoid excessive re-renders on room list store update or filter change

[florianduros]

May fix #32574
Needs #32677 to fix EC tests

• Don't clear all the item vms on room list update. Only on space change
• Avoid to clear all the items vms when changing filters
• Avoid to re-render all the filters on room list update

Room list item vms are cleared when scrolling:

element-web/apps/web/src/viewmodels/room-list/RoomListViewViewModel.ts

Lines 200 to 218 in 3fb99fe

	/**
	* Update which rooms are currently visible.
	* Called by the view when scroll position changes.
	* Disposes of view models for rooms no longer visible.
	*/
	public updateVisibleRooms(startIndex: number, endIndex: number): void {
	const allRoomIds = this.roomIds;
	const newVisibleIds = allRoomIds.slice(startIndex, Math.min(endIndex, allRoomIds.length));
	const newVisibleSet = new Set(newVisibleIds);
	// Dispose view models for rooms no longer visible
	for (const [roomId, viewModel] of this.roomItemViewModels.entries()) {
	if (!newVisibleSet.has(roomId)) {
	viewModel.dispose();
	this.roomItemViewModels.delete(roomId);
	}
	}
	}

Before (start at 20sec)

Screen.Recording.2026-02-26.at.18.37.01.mov

After

Untitled.mov

[langleyd]

I suppose the flip side of this is that some of these VMs will had around int he map until removed. But as you said when the visible rooms change they will be cleaned up.

[t3chguy]

Looks sane