Refactor Container to support atomic component moves

Input from Gemini 3 Pro:

✦ I have successfully refactored Neo.container.Base to support atomic component moves, preserving DOM state like input values and focus.

Key Changes:

1. Container.Base.insert:

   • Refactored to handle moving existing NeoInstance items.
   • Implemented "Silent Remove + Update New Parent" strategy.
   • Calls oldParent.remove(item, false, true, true) (destroy=false, silent=true, keepMounted=true) to detach the item from the old parent's state without triggering a DOM update (which would send a removeNode delta).
   • Then, it updates the new parent (me). The VDOM diff generates an insertNode delta. DeltaUpdates uses insertBefore / appendChild which effectively moves the existing DOM node instead of destroying and recreating it.

2. Container.Base.remove / removeAt:

   • Added keepMounted argument to prevent item.mounted = false during the silent move process. This is critical to keep the component's lifecycle active.

3. Neo.worker.App.moveComponent:

   • Simplified to delegate the atomic move logic entirely to parent.insert (or parent.add).
   • Restored guardrails for component, parent existence, and parent.isContainer.

4. Neo.main.DeltaUpdates.moveNode:

   • Addressed a critical browser behavior (Chromium/WebKit) where reparenting a focused element causes it to lose focus (blur event).
   • Implemented logic to capture document.activeElement before the move.
   • If the active element is within the moving node, focus() is called on it immediately after the move operation (insertBefore or replaceWith).
   • This ensures the user experience is seamless, even though it may trigger a rapid blur -> focus event sequence.

Verification:

• Created a new Playwright test suite test/playwright/component/container/AtomicMoves.spec.mjs.
• Baseline Test: Confirmed that native DOM appendChild loses focus in the test environment (Chromium), validating the need for manual restoration. Also confirmed moveBefore (if available) would preserve it.
• Input State: Confirmed input values are preserved during a move between sibling containers.
• Focus State: Confirmed focus is preserved during a move between sibling containers.
• DOM State: Confirmed custom DOM properties are preserved.

The feature is implemented and robustly tested.

Input from Gemini 3 Pro:

✦ I have updated the JSDoc for Neo.container.Base, Neo.worker.App, and Neo.main.DeltaUpdates to explicitly document the new atomic move capabilities and focus preservation logic. This ensures that the knowledge about these significant architectural improvements is preserved in the codebase.