grammar+db: 3g — RETURNING on INSERT/UPDATE/DELETE (ADR-0033 §5)

Shared RETURNING_CLAUSE (reuses Phase-2 PROJECTION_LIST, now
pub(crate)) as an optional tail on all three SQL DML shapes.
`returning: bool` on the Command variants, set by the ast-builders
and threaded to the worker. run_returning collects the returned rows
as a DataResult (RETURNING mutates + yields in one pass), reusing
resolve_select_column_types for bare-column type recovery; computed
projections stay typeless. DeleteResult gains a `data` field rendered
alongside the cascade summary.

Follow-set fix: `returning` is added to the table-source and
projection bare-alias follow-sets so an INSERT … SELECT row source
stops before RETURNING instead of reading it as a table alias.

Auto-fill × RETURNING: build_sql_insert stops row_source before the
RETURNING token (keeping it preparable for shortid materialisation),
and plan_shortid_autofill re-appends the RETURNING tail so generated
shortids surface in RETURNING *.

Tests (+17): grammar accept on all three; INSERT/UPDATE/DELETE
RETURNING incl. *, aliases, multi-row, type recovery + computed-
typeless; auto-fill × RETURNING (single + multi-row distinct ids);
INSERT…SELECT…RETURNING execution; UPDATE…RETURNING zero-match;
DELETE…RETURNING cascade+rows; app-level render of both. Dev
sql_insert/sql_update/sql_delete entry words still removed in 3j.
1562 pass / 0 fail / 1 ignored. Clippy clean.

src/dsl/command.rs

@@ -311,6 +311,11 @@ pub enum Command {
         target_table: String,
         listed_columns: Vec<String>,
         row_source: String,
+        /// Whether a `RETURNING` clause matched (ADR-0033 §5,
+        /// sub-phase 3g). The worker collects the returned rows as a
+        /// `DataResult` when true; otherwise it surfaces the
+        /// affected-row count (+ auto-show) as before.
+        returning: bool,
     },
     /// A SQL `UPDATE` validated by the walker (ADR-0033 §2,
     /// advanced mode). Grammar-as-text: the worker executes `sql`
@@ -319,6 +324,9 @@ pub enum Command {
     SqlUpdate {
         sql: String,
         target_table: String,
+        /// Whether a `RETURNING` clause matched (ADR-0033 §5,
+        /// sub-phase 3g).
+        returning: bool,
     },
     /// A SQL `DELETE` validated by the walker (ADR-0033 §1/§7,
     /// advanced mode). Grammar-as-text: the worker executes `sql`,
@@ -331,6 +339,10 @@ pub enum Command {
     SqlDelete {
         sql: String,
         target_table: String,
+        /// Whether a `RETURNING` clause matched (ADR-0033 §5,
+        /// sub-phase 3g). The cascade summary surfaces alongside the
+        /// returned rows when true.
+        returning: bool,
     },
     /// App-lifecycle command (per ADR-0003). These work in both
     /// simple and advanced modes; the dispatcher branches on the