Refactor Store: Default to eager record init for DX and enhance JSDoc

Refactor Neo.data.Store to default add() and insert() to eager record initialization (init=true) and enhance JSDoc.

Reasoning (DX): The previous default behavior of add() returning raw data objects (lazy loading) was a common "gotcha" for developers, requiring a second step (store.get(id)) to obtain a usable Model instance. By changing the default init parameter to true, store.add(data) now returns fully instantiated records by default, which is the expected behavior in most standard use cases.

Changes:

1. Neo.data.Store:
   • add(item, init=true): Defaults to eager initialization.
   • insert(index, item, init=true): Defaults to eager initialization.
   • Internal usages (afterSetData, sort) explicitly use init=false to preserve performance for bulk operations.
2. examples/grid/bigData/MainStore.mjs:
   • Explicitly uses init=false ("Turbo Mode") to ensure the 100k row benchmark continues to use the performant lazy-loading chunking mechanism.

Documentation Enhancement: The JSDoc for add and insert in Neo.data.Store needs to be significantly enhanced to clearly explain:

• The difference between init=true (eager, returns Records) and init=false (lazy, returns raw data / count).
• The performance implications (use init=false for bulk loading).
• The return type variations (Number vs Array).