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/grammar/data.rs

@@ -890,10 +890,19 @@ fn build_sql_insert(path: &MatchedPath, source: &str) -> Result<Command, Validat
             _ => None,
         })
         .collect();
-    // The row source is everything from the `VALUES` / `SELECT` /
-    // `WITH` keyword onward. Located by the first matching *Word
-    // token* in the path (not a text scan), so a string literal
-    // like `values ('select')` can't be mistaken for the keyword.
+    // The row source is the `VALUES` / `SELECT` / `WITH` clause —
+    // from that keyword up to (but not including) any `RETURNING`
+    // tail (3g) or trailing `;`. Both boundaries are located by
+    // *Word token* in the path (not a text scan), so a string
+    // literal like `values ('select')` / `values ('returning')`
+    // can't be mistaken for a keyword. Excluding RETURNING keeps the
+    // row source independently preparable for `shortid` auto-fill
+    // (`VALUES … RETURNING …` is not a valid standalone statement).
+    let returning_start = path
+        .items
+        .iter()
+        .find(|item| matches!(item.kind, MatchedKind::Word("returning")))
+        .map(|item| item.span.0);
     let row_source = path
         .items
         .iter()
@@ -901,7 +910,8 @@ fn build_sql_insert(path: &MatchedPath, source: &str) -> Result<Command, Validat
             matches!(item.kind, MatchedKind::Word("values" | "select" | "with"))
         })
         .map(|item| {
-            source[item.span.0..]
+            let end = returning_start.unwrap_or(source.len());
+            source[item.span.0..end]
                 .trim()
                 .trim_end_matches(';')
                 .trim()
@@ -920,9 +930,21 @@ fn build_sql_insert(path: &MatchedPath, source: &str) -> Result<Command, Validat
         target_table,
         listed_columns,
         row_source,
+        returning: path_has_returning(path),
     })
 }
 
+/// Whether the matched path contains a `RETURNING` clause
+/// (ADR-0033 §5, sub-phase 3g). Located by the `returning` *Word
+/// token* in the path — path-based, so a string literal can't be
+/// mistaken for the keyword (mirrors `build_sql_insert`'s
+/// row-source detection).
+fn path_has_returning(path: &MatchedPath) -> bool {
+    path.items
+        .iter()
+        .any(|item| matches!(item.kind, MatchedKind::Word("returning")))
+}
+
 /// Build `Command::SqlUpdate` from a validated SQL `UPDATE`
 /// (ADR-0033 §2, sub-phase 3e). Extracts the target table from the
 /// matched path so the worker re-persists the right CSV.
@@ -949,7 +971,11 @@ fn build_sql_update(path: &MatchedPath, source: &str) -> Result<Command, Validat
         .first()
         .map_or(source, |entry| &source[entry.span.1..]);
     let sql = format!("update {}", tail.trim());
-    Ok(Command::SqlUpdate { sql, target_table })
+    Ok(Command::SqlUpdate {
+        sql,
+        target_table,
+        returning: path_has_returning(path),
+    })
 }
 
 /// Build `Command::SqlDelete` from a validated SQL `DELETE`
@@ -982,7 +1008,11 @@ fn build_sql_delete(path: &MatchedPath, source: &str) -> Result<Command, Validat
         .first()
         .map_or(source, |entry| &source[entry.span.1..]);
     let sql = format!("delete {}", tail.trim());
-    Ok(Command::SqlDelete { sql, target_table })
+    Ok(Command::SqlDelete {
+        sql,
+        target_table,
+        returning: path_has_returning(path),
+    })
 }
 
 // =================================================================