feat: ADR-0036 Phase 1 — validate advanced-mode INSERT literals + show the value

Capture literal VALUES at parse onto Command::SqlInsert (no grammar change,
no reparse); validate them against column types before the still-verbatim
insert (reusing impl_value_for for DSL-parity wording); read them in the
error enricher so a constraint error names the real value. Execution,
auto-fill, and command identity unchanged. Adds run_sql_insert_with_literals
(runtime path); run_sql_insert stays the no-capture raw entry.

Proven: malformed date 2025/01/15 now refused in advanced-mode SQL; replayed
UNIQUE shows the real value. Tests +3 (expression runs, multi-row, natural
order) + 2 flipped/strengthened. 1930 pass / 0 fail / 0 skip; clippy clean.

src/runtime.rs

@@ -1570,6 +1570,19 @@ fn user_value_for_column(command: &Command, column: &str) -> Option<crate::dsl::
             .iter()
             .find(|(c, _)| c == column)
             .map(|(_, v)| v.clone()),
+        // ADR-0036 Phase 1: a single-row literal SQL INSERT retains its
+        // captured literals, so a constraint error can name the real
+        // value. Explicit column list only here (natural order needs the
+        // schema); multi-row is skipped (which row conflicted is
+        // ambiguous) — both degrade to the neutral "that value".
+        Command::SqlInsert {
+            listed_columns,
+            literal_rows,
+            ..
+        } if literal_rows.len() == 1 && !listed_columns.is_empty() => {
+            let idx = listed_columns.iter().position(|c| c == column)?;
+            literal_rows[0].get(idx).cloned().flatten()
+        }
         _ => None,
     }
 }
@@ -2236,8 +2249,17 @@ async fn execute_command_typed(
             listed_columns,
             row_source,
             returning,
+            literal_rows,
         } => database
-            .run_sql_insert(sql, src, target_table, listed_columns, row_source, returning)
+            .run_sql_insert_with_literals(
+                sql,
+                src,
+                target_table,
+                listed_columns,
+                row_source,
+                returning,
+                literal_rows,
+            )
             .await
             .map(CommandOutcome::Insert),
         // A SQL `UPDATE` (advanced mode; ADR-0033 §2). Grammar-as-