feat(markdown): support yaml role=tag info string

Accept yaml role=tag alongside legacy yaml/tag so the block
body gets yaml syntax highlighting, matching the CLI role=
attribute convention. Copy button now emits the role=tag form.

src/components/md-deck/hooks/deckStore.ts

@@ -521,7 +521,7 @@ export function createDeckStore(initialSrc: string = ""): DeckStore {
     return parts.join("");
   };
 
-  /** Serialize the deck back to a ```yaml/tag codeblock (round-trips templates). */
+  /** Serialize the deck back to a yaml codeblock (round-trips templates). */
   const generateYamlCode = () => {
     const toYamlLayer = (l: LayerConfig) => {
       const out: Record<string, unknown> = {};
@@ -560,8 +560,9 @@ export function createDeckStore(initialSrc: string = ""): DeckStore {
       lineWidth: -1,
       noRefs: true,
     });
-    const fence = "```";
-    return `${fence}yaml/tag\n${yamlStr}${fence}`;
+    const fence = "```yaml role=tag";
+    const backtick = "`";
+    return `${fence}\n${yamlStr}${backtick.repeat(3)}`;
   };
 
   const copyCode = async (fallback?: (code: string) => void) => {