grammar+db: 3b — SQL INSERT grammar + minimal execution (ADR-0033 §1)

SQL_INSERT_SHAPE (INTO <table> [(cols)] VALUES tuple(s)) with __rdbms_*
target rejection; Command::SqlInsert{sql,target_table}; Request::RunSqlInsert
+ do_sql_insert worker (tx-guarded: execute, then finalize_persistence for
CSV + history before commit, so failures roll back and don't re-persist).
Auto-show is best-effort via last_insert_rowid range.

Isolated behind a dev `sqlinsert` entry word (Advanced) so the SQL path is
testable without making `insert` a shared word yet (that's 3j, after 3d
auto-fill parity). Command::SqlInsert carries only sql+target_table; the
plan's listed_columns/returning land in 3d/3g where they're read.

6 grammar accept/reject tests + 8 integration tests (single/multi-row,
column-list, full-arity, history, rollback-on-failure, multi-row atomicity,
parse-path reconstruction, internal-table rejection). 1452 baseline green.

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_insert;
 pub mod sql_select;
 
 use crate::dsl::command::Command;
@@ -570,6 +571,10 @@ pub static REGISTRY: &[(&CommandNode, CommandCategory)] = &[
     (&data::EXPLAIN, CommandCategory::Simple),
     (&data::SELECT, CommandCategory::Advanced),
     (&data::WITH, CommandCategory::Advanced),
+    // SQL INSERT development scaffold (sub-phase 3b–3i); the
+    // temporary `sqlinsert` entry word keeps it isolated from the
+    // DSL `insert` word until 3j wires the shared entry.
+    (&data::SQL_INSERT, CommandCategory::Advanced),
 ];
 
 /// Whether `entry` names an advanced-mode-only command (ADR-0030