TreeGrid: Fix 7-click expand/collapse bug and redundant change events

Problem

Users reported a bug in the TreeGrid where clicking an expand/collapse icon required 7 clicks before the icon visually updated to reflect the new state, even though rows were added/removed correctly on the first click.

Analysis

The TreeStore.mjs expand and collapse methods were manually firing me.onRecordChange immediately after mutating a node property (e.g., node.collapsed = false). However, since node is guaranteed to be a fully hydrated Record instance (via me.get()), the property mutation itself already triggers the notifyChange setter in RecordFactory, which increments record.version and fires onRecordChange natively.

The duplicate, manual onRecordChange call fired a second event without incrementing the record.version. This caused a race condition in grid.Body and Component.mjs#cellRenderer, where the VDOM update short-circuited because component.lastRecordVersion === record.version. The 7 clicks forced a row recycle, bypassing the short-circuit and finally updating the DOM.

Solution

1. Removed all redundant manual me.onRecordChange calls in collapse() and expand().
2. Changed single-property updates to direct assignment (node.collapsed = true), relying on the RecordFactory setter.
3. Changed multi-property async updates to use batched assignment (node.set({ isLoading: false, collapsed: false })) to fire a single, clean mutate event.
4. Added an E2E test (GridTree.spec.mjs) to verify the correct node expand/collapse behavior on the first click.