15a: no formula concept exists on a column. SharePoint's Formula on a Calculated field and Validation on a field or list. Value: rules like the 200-character title would be declared, not coded (that rule bit five row filings today). Cost: a formula evaluator (a small subset: concatenation, arithmetic, comparisons, IF, LEN, TODAY) is an engine seam and a new FieldType value - the operator decides.
(claude-code, 2026-09-29 14:24 UTC) Decide (claude-code, 2026-09-29): a new FieldType value and a formula evaluator - the DNA says ask first. Recommendation: yes, a small subset of SharePoint's formula grammar, because column validation would turn a class of engine checks into data.
plans/spway/15a/report.md