Matrix: insert Form C + update + delete coverage

34 new tests covering:
- Form C bare-value-list (happy path + Form-A-recovery + type-unaware grammar limitation per handoff §2.2)
- update with WHERE (column-narrowing invariant per handoff §1 bug E1; typed-slot prose for assignments and where filters)
- update --all-rows (filter-clause requirement per ADR-0014)
- delete with WHERE (column-narrowing; typed-slot prose for where filters)
- delete --all-rows

859 baseline -> 931 passing. No bugs surfaced — the data-mutation
command family was already well-shaped post-Phase-D.

tests/typing_surface/delete_all_rows.rs

@@ -1 +1,30 @@
-//! Submodule stub — populated in subsequent tasks.
+//! Matrix coverage for `delete from T --all-rows` (ADR-0014).
+
+use crate::typing_surface::*;
+use rdbms_playground::input_render::InputState;
+
+#[test]
+fn complete_delete_all_rows_parses() {
+    let schema = schema_serial_pk();
+    let a = assess_at_end("delete from Customers --all-rows", &schema);
+    assert!(matches!(a.state, InputState::Valid));
+    assert_eq!(a.parse_result.as_deref(), Ok("Delete"));
+    crate::snap!("complete_all_rows", a);
+}
+
+#[test]
+fn delete_without_filter_clause_is_incomplete() {
+    // Per ADR-0014 — delete requires WHERE or --all-rows.
+    let schema = schema_serial_pk();
+    let a = assess_at_end("delete from Customers", &schema);
+    assert!(matches!(a.state, InputState::IncompleteAtEof));
+    crate::snap!("no_filter", a);
+}
+
+#[test]
+fn delete_partial_flag_is_incomplete() {
+    let schema = schema_serial_pk();
+    let a = assess_at_end("delete from Customers --all", &schema);
+    assert!(!matches!(a.state, InputState::Valid));
+    crate::snap!("partial_flag", a);
+}