feat(hint): H2 Phase C batch 3 — DML tier-3 hints (ADR-0053)

Per-form hints for querying/changing data: update, delete, show
data/table/tables/relationships/indexes, seed, explain, replay
(insert was the Phase-B exemplar). hint_ids wired on UPDATE/DELETE/
SHOW/SEED/EXPLAIN/REPLAY; catalogue + keys.rs registered. +2 spot
tests (incl. multi-form SHOW disambiguation); 2493 pass / 1 ignored,
clippy clean.

src/app.rs

@@ -5882,6 +5882,25 @@ mod tests {
         assert!(!output_contains(&app, "Remove a table"));
     }
 
+    // ── Phase C batch 3: DML hints render (incl. multi-form SHOW) ──
+
+    #[test]
+    fn f1_on_update_renders_its_hint_block() {
+        let mut app = App::new();
+        type_str(&mut app, "update Customers set email = 'x' ");
+        f1(&mut app);
+        assert!(output_contains(&app, "Change values in the rows"));
+    }
+
+    #[test]
+    fn f1_disambiguates_show_forms() {
+        let mut app = App::new();
+        type_str(&mut app, "show relationships");
+        f1(&mut app);
+        assert!(output_contains(&app, "List all the relationships"));
+        assert!(!output_contains(&app, "rows stored in a table"));
+    }
+
     #[test]
     fn messages_command_toggles_verbosity_and_reports() {
         let mut app = App::new();