Fix VDOM initialization race condition causing child update collisions

A race condition exists in src/mixin/VdomLifecycle.mjs where child components can trigger VDOM updates concurrently with their parent's initialization phase (initVnode).

The Issue:

1. initVnode sets me.isVdomUpdating = true but fails to register the update with the global VDomUpdate manager.
2. Consequently, the hierarchical safeguard isParentUpdating fails for child components because VDomUpdate.getInFlightUpdateDepth(parent.id) returns undefined.
3. Additionally, me.isVdomUpdating is set to false prematurely in initVnode, before the component is mounted and the update promise is resolved.

Symptoms:

• Child components triggering updates (e.g., via vnodeInitialized hooks) collide with the parent's ongoing initialization.
• This can lead to state desynchronization with the VDOM worker, resulting in duplicate DOM insertions (as seen in Panel components duplicating headers/bodies).

Proposed Fix:

1. Register In-Flight Update: initVnode must call VDomUpdate.registerInFlightUpdate(me.id, -1) to formally lock the tree.
2. Centralize Cleanup: Move me.isVdomUpdating = false into resolveVdomUpdate to ensure the flag remains true until the entire transaction (including callbacks and mounting) is complete.
3. Refactor: Update executeVdomUpdate to rely on resolveVdomUpdate for clearing the flag, ensuring consistency.