Sorting columns with mapped data and missing values (like company in DevIndex) resulted in unstable, varying sort orders that seemingly "improved" the more times a sort was triggered.

This occurred due to two overlapping issues:

1. Soft Hydration Inconsistency: Neo.data.Store#resolveField was returning undefined for missing mapped keys on raw objects, while fully hydrated records correctly received their defaultValue (e.g., null).
2. JavaScript Sorting Transitivity: Neo.collection.Base and Neo.collection.Sorter relied on standard < and > operators. In JS, null and undefined evaluate as "equal" to strings (both < and > return false), breaking sorting transitivity and causing random scrambling of the array.

This ticket fixes the bug by introducing an enhancement to the framework's sorting paradigm: null and undefined values are now always pushed to the bottom of the collection, regardless of whether the sort direction is ASC or DESC.

Changes:

• src/data/Store.mjs: Updated resolveField() to apply defaultValue if the raw value is undefined.
• src/collection/Base.mjs: Added explicit == null isolation logic to doSort() to always push null/undefined values to the bottom.
• src/collection/Sorter.mjs: Added explicit == null isolation logic to defaultSortBy() to always push null/undefined values to the bottom.
• test/playwright/unit/collection/SortNull.spec.mjs: Added a new unit test to explicitly verify this behavior.