grammar+db: 3f — SQL DELETE + cascade summary (ADR-0033 §1/§7)

New src/dsl/grammar/sql_delete.rs (FROM <table> [WHERE] [;]),
Command::SqlDelete, Request::RunSqlDelete, do_sql_delete worker.

do_sql_delete mirrors the DSL do_delete: detect FK cascade by
before/after child row-count diffing, re-persist target + every
cascade-affected child, history-on-success inside the tx. Reuses
CommandOutcome::Delete -> handle_dsl_delete_success, so the
per-relationship cascade summary formatter is shared, not duplicated.

ADR-0033 Amendment 2: supersedes §7's WHERE-injected pre-count. Its
premise (DSL handler builds pre-counts from the typed Expr) was wrong
— do_delete uses count-diff. The pre-count would also have broken the
§2 parity promise by reporting SET NULL the DSL path doesn't. Count-
diff gives exact parity, no WHERE-byte extraction, and withdraws R2.
SET NULL reporting deferred for both paths (user-confirmed).

Tests: +6 grammar unit, +12 integration (cascade parity with DSL,
both R2 subquery cases, before-execute order, no-WHERE, FK-rejection
rollback, childless-parent, two-child cascade). 1542 pass / 0 fail /
1 ignored. Clippy clean. Dev sql_delete entry word removed in 3j.

src/dsl/grammar/mod.rs

@@ -28,6 +28,7 @@ pub mod ddl;
 pub mod expr;
 pub mod shared;
 pub mod sql_expr;
+pub mod sql_delete;
 pub mod sql_insert;
 pub mod sql_select;
 pub mod sql_update;
@@ -580,6 +581,10 @@ pub static REGISTRY: &[(&CommandNode, CommandCategory)] = &[
     // `sql_update` entry word keeps it isolated from the DSL
     // `update` word until 3j wires the shared entry.
     (&data::SQL_UPDATE, CommandCategory::Advanced),
+    // SQL DELETE development scaffold (sub-phase 3f); the temporary
+    // `sql_delete` entry word keeps it isolated from the DSL
+    // `delete` word until 3j wires the shared entry.
+    (&data::SQL_DELETE, CommandCategory::Advanced),
 ];
 
 /// Whether `entry` names an advanced-mode-only command (ADR-0030