feat(hint): H2 Phase C batch 2 — DDL tier-3 hints (ADR-0053)

Per-form hints for the schema-shaping commands: create table, create
m:n, add column/index/constraint, drop table/column/relationship/
index/constraint, rename column, change column (add_relationship was
the Phase-B exemplar). Examples verified against the canonical usage
templates. hint_ids wired on CREATE/CREATE_M2N/DROP/RENAME/CHANGE;
catalogue + keys.rs registered. +2 spot tests (incl. multi-form DROP
disambiguation); 2491 pass / 1 ignored, clippy clean.

src/dsl/grammar/ddl.rs

@@ -968,7 +968,13 @@ pub static DROP: CommandNode = CommandNode {
     shape: DROP_SHAPE,
     ast_builder: build_drop,
     help_id: Some("ddl.drop"),
-    hint_ids: &[],
+    hint_ids: &[
+        "drop_table",
+        "drop_column",
+        "drop_relationship",
+        "drop_index",
+        "drop_constraint",
+    ],
     usage_ids: &[
         "parse.usage.drop_table",
         "parse.usage.drop_column",
@@ -1004,7 +1010,7 @@ pub static RENAME: CommandNode = CommandNode {
     shape: RENAME_COLUMN,
     ast_builder: build_rename_column,
     help_id: Some("ddl.rename"),
-    hint_ids: &[],
+    hint_ids: &["rename_column"],
     usage_ids: &["parse.usage.rename_column"],};
 
 pub static CHANGE: CommandNode = CommandNode {
@@ -1012,7 +1018,7 @@ pub static CHANGE: CommandNode = CommandNode {
     shape: CHANGE_COLUMN,
     ast_builder: build_change_column,
     help_id: Some("ddl.change"),
-    hint_ids: &[],
+    hint_ids: &["change_column"],
     usage_ids: &["parse.usage.change_column"],};
 
 // =================================================================
@@ -1373,7 +1379,7 @@ pub static CREATE: CommandNode = CommandNode {
     shape: CREATE_TABLE,
     ast_builder: build_create_table,
     help_id: Some("ddl.create"),
-    hint_ids: &[],
+    hint_ids: &["create_table"],
     usage_ids: &["parse.usage.create_table"],};
 
 // =================================================================
@@ -1442,7 +1448,7 @@ pub static CREATE_M2N: CommandNode = CommandNode {
     shape: CREATE_M2N_SHAPE,
     ast_builder: build_create_m2n,
     help_id: Some("ddl.create_m2n"),
-    hint_ids: &[],
+    hint_ids: &["create_m2n"],
     usage_ids: &["parse.usage.create_m2n"],
 };