SQL `SELECT *` omits `@computed` scalars (`subtotal=undefined`) while an explicit column list surfaces them corr

From dispatch finding (task `qa-wave-2026072920`):

- F-257 — SQL `SELECT *` omits `@computed` scalars (`subtotal=undefined`) while an explicit column list surfaces them correctly (`subtotal=10`), and REST's default no-select GET plus GraphQL both work — so the wildcard path was missed by #1484/#1601 (`c899a82a2`), whose stated scope was "default reads across REST/GraphQL/SQL". Two days post-merge is the cheapest moment to close it. Distinct code path from F-190, which drops *dynamic* attributes on schema-less tables; these two only share a symptom surface.
Related to https://github.com/HarperFast/harper/issues/2296

Start by tracing the SQL SELECT * wildcard path for @computed scalars, then compare it with the explicit-column path and the REST default no-select and GraphQL entry points. Done means a wildcard SQL read returns subtotal (10 in the reported case) rather than undefined, without regressing explicit columns; use the behavior in the issue as the check.

Written by the indexing model from the issue text.