grammar+db: 3e — SQL UPDATE grammar + execution (ADR-0033 §2)

New src/dsl/grammar/sql_update.rs: SQL_UPDATE_SHAPE =
<table> SET col = sql_expr (',' …)* [WHERE sql_expr] [';'], the
__rdbms_* target rejection, and the shared sql_expr on both the
assignment RHS and the predicate. No --all-rows rail — a SQL
UPDATE without WHERE runs as written (ADR-0030 §12). Reuses
sql_select::WHERE_CLAUSE (now pub(crate)) so the predicate
diagnostics are identical. The target uses the shared `table_name`
ident role (not a bespoke one) so the Phase-2 schema-existence and
predicate-warning passes collect it as a scope binding and check
the SET / WHERE columns for free — a bespoke role left them
unchecked (the cross-cut tests caught this).

Command::SqlUpdate { sql, target_table }; Request::RunSqlUpdate +
do_sql_update (execute validated SQL via execute_with_fk_enrichment,
re-persist the target CSV, append history.log). 3e surfaces the
affected-row count only; precise row output is RETURNING (3g), so
the update-success render skips a column-less data set rather than
showing a misleading "(no rows)" band. Behind the dev `sql_update`
entry word until 3j.

Tests: grammar accept/reject; integration (single/multi-col,
no-WHERE all-rows, sql_expr in SET, scalar subquery in SET,
zero-match success, history); walker cross-cut (unknown SET column
→ unknown_column, `= NULL` in WHERE → eq_null warning); app-level
render-guard both ways (column-less → count only; with columns →
table renders). 1524 green, clippy clean.

src/runtime.rs

@@ -1894,6 +1894,14 @@ async fn execute_command_typed(
             .run_sql_insert(sql, src, target_table, listed_columns, row_source)
             .await
             .map(CommandOutcome::Insert),
+        // A SQL `UPDATE` (advanced mode; ADR-0033 §2). Grammar-as-
+        // text: the worker runs the validated `sql` and re-persists
+        // the parsed `target_table`'s CSV. Reuses the DSL update
+        // outcome (affected-row count).
+        Command::SqlUpdate { sql, target_table } => database
+            .run_sql_update(sql, src, target_table)
+            .await
+            .map(CommandOutcome::Update),
         // `EXPLAIN QUERY PLAN` never executes the wrapped
         // statement (ADR-0028 §2), so explaining a destructive
         // command is safe. `src` is unused here — explain is a