test+docs: 3k Phase-3 verification sweep — e2e DML + filled cross-cut matrix

Sub-phase 3k of ADR-0033. Adds the Tier-3 end-to-end DML suite (tests/sql_dml_e2e.rs) and the cross-cut gap-fill tests, fills the verification matrix (every row a verified file::function), and produces the phase-exit report.

- tests/sql_dml_e2e.rs: INSERT…SELECT cross-table, all-ten-type multi-row INSERT + RETURNING type recovery, UPDATE-with-subquery-in-SET, cascade DELETE, UPSERT round-trip, RETURNING x3, history.log replay, OOS rejections (full §13 table), validity-indicator-from-SQL-DML.
- walker/mod.rs, highlight.rs, completion.rs, input_render.rs: inherited-diagnostic, DML-keyword highlight, INSERT INTO completion, and advanced-mode DML hint-panel cross-cuts.
- Matrix correction (user-confirmed): predicate warnings fire on row-scoped DML slots; INSERT VALUES has no row scope (ADR-0033 §8.4).
- Auto-snapshot row marked N/A (user-confirmed): ADR-0006 unimplemented for both paths; deferred.

/runda round: added an advanced-mode DML hint-panel test (A6 was attributed to simple-mode prose under the §8 advanced heading); extended OOS coverage to the full ADR-0033 §13 table (OOS-5 INDEXED BY / OOS-6 multi-statement) + a trailing-semicolon guard.

1645 passing / 0 failing / 0 skipped / 1 ignored. Clippy clean.

src/completion.rs

@@ -1896,6 +1896,20 @@ mod tests {
         assert_eq!(cs, vec!["Customers".to_string(), "Orders".to_string()]);
     }
 
+    #[test]
+    fn insert_into_offers_table_names_at_target_slot() {
+        // 3k cross-cut (matrix A3): after `insert into ` the target
+        // table slot completes to the schema's table names.
+        let cache = SchemaCache {
+            tables: vec!["Customers".to_string(), "Orders".to_string()],
+            columns: vec![],
+            relationships: vec![],
+            ..SchemaCache::default()
+        };
+        let cs = cands_with("insert into ", 12, &cache);
+        assert_eq!(cs, vec!["Customers".to_string(), "Orders".to_string()]);
+    }
+
     #[test]
     fn schema_cache_offers_column_names_at_column_slot() {
         let cache = SchemaCache {