Problem

The aggregate function reference does not describe IvorySQL Oracle-compatible LISTAGG, its grouped and analytic forms, result limit, ordering behavior, or unsupported Oracle clauses.

Proposed change

Add syntax, examples, semantics, errors, and compatibility notes to the aggregate function documentation.

Acceptance criteria

• Grouped and analytic usage are covered.
• Ordering, null handling, and the result-size limit are clear.
• Unsupported syntax is identified.
• The complete SGML validation passes.