fix(markdown): accept tilde fences when scanning

Fenced block scanning was backtick-only in FENCED_BLOCK_RE (used by scanDoc) and in the yaml role=tag render extension, while stripFencedBlocks and the validator already accepted tildes. Match both marker styles and require the closing fence to reuse the opening marker.

src/markdown/code-block-yaml-tag.test.ts

@@ -70,6 +70,16 @@ describe("code-block-yaml-tag", () => {
     expect(token).toBeUndefined();
   });
 
+  test("supports tilde fences", () => {
+    const html = render("~~~yaml role=tag\ntag: md-deck\nbody: ./cards.csv\n~~~");
+    expect(html).toContain("<md-deck>./cards.csv</md-deck>");
+  });
+
+  test("does not swallow plain tilde yaml code blocks", () => {
+    const token = ext.tokenizer("~~~yaml\nsize: 54x86\n~~~");
+    expect(token).toBeUndefined();
+  });
+
   test("does not swallow yaml blocks without role=tag", () => {
     const token = ext.tokenizer("```yaml tag=md-deck\nsize: 54x86\n```");
     expect(token).toBeUndefined();

src/markdown/code-block-yaml-tag.ts

@@ -13,7 +13,7 @@ import { parseBlockAttrs } from "./block-attrs.js";
  * `role=tag` on the info string marks the block (and lets the content
  * scanner keep it intact). `tag=` / `id=` / any other `key=value` fence
  * attributes override the same keys in the YAML body, so simple cases
- * stay on one line.
+ * stay on one line. Both backtick and tilde fences are accepted.
  */
 export default function markedCodeBlockYamlTag(): MarkedExtension {
   return {
@@ -22,13 +22,13 @@ export default function markedCodeBlockYamlTag(): MarkedExtension {
         name: "code-block-yaml-tag",
         level: "block",
         start(src: string) {
-          return src.match(/^```yaml\s+role=tag(?:\s|\n)/m)?.index;
+          return src.match(/^(?:`{3,}|~{3,})yaml\s+role=tag(?:\s|\n)/m)?.index;
         },
         tokenizer(src: string) {
-          const rule = /^```yaml\s+role=tag([^\n]*)\n([\s\S]*?)\n```/;
+          const rule = /^([`~])\1{2,}yaml\s+role=tag([^\n]*)\n([\s\S]*?)\n\1{3,}/;
           const match = rule.exec(src);
           if (match) {
-            const yamlContent = match[2]?.trim() || "";
+            const yamlContent = match[3]?.trim() || "";
             let yamlProps: Record<string, unknown> = {};
             try {
               yamlProps =
@@ -39,7 +39,7 @@ export default function markedCodeBlockYamlTag(): MarkedExtension {
             }
 
             // Fence attributes override YAML body values.
-            const attrs = parseBlockAttrs(match[1] || "");
+            const attrs = parseBlockAttrs(match[2] || "");
             const fenceProps: Record<string, unknown> = {
               ...(attrs.id ? { id: attrs.id } : {}),
               ...attrs.extra,