docs(driver.sql): topByTimestamp is only defined when the ordering column is unique (Driver.Sql-008)

docs/drivers/Sql.md

@@ -80,6 +80,14 @@ the nested form.
 }
 ```
 
+⚠️ **`topByTimestamp` needs an ordering column that is unique per row.** It is executed as an
+`ORDER BY <column> DESC` with the dialect's single-row limit, so when the column ties the server
+returns an arbitrary row among the tied ones — and the driver cannot warn about it, because the other
+rows were discarded before the result set reached it (the `whereColumn`/`whereValue` form *does*
+warn, on `Rows.Count > 1`). A `date`-typed column ties for every row written on the same day, and
+browse-commit will nominate one. Prefer a `datetime2`/sequence column that is unique per row, or
+point the tag at a latest-row view.
+
 `whereValue` may be authored as a JSON string, number or boolean (it is bound as a parameter either
 way). `keyValue` on the `KeyValue` model must be a **string**.