MemWAL in-memory FTS currently supports Utf8, LargeUtf8, and Utf8View columns. Persisted FTS indexes are gaining row-level document semantics for list string columns, so MemWAL should be evaluated and updated separately to keep fresh-tier FTS behavior consistent when list string rows are served from MemWAL.

Scope:

• Support List<Utf8>, List<LargeUtf8>, LargeList<Utf8>, and LargeList<LargeUtf8> in the MemWAL FTS indexing path.
• Use row-level document semantics: one list row is one document, and non-null elements are text fragments in that document.
• Keep null list rows, empty lists, and all-null element lists non-matching.
• Preserve the no-gap list position behavior if phrase queries are supported for this path.
• Add MemWAL FTS tests for list row-level matching and phrase matching across list elements.