refactor(markdown): unify yaml tag block syntax on role=tag

Drop legacy yaml/tag info string; tag blocks now require
```yaml role=tag. Add fence-line tag=/id= attributes that
override YAML body values, and move parseBlockAttrs to
src/markdown/block-attrs.ts so scanner and render extensions
share one parser.

src/cli/completions/block-scanner.ts

@@ -7,20 +7,12 @@
  * - `role` dispatches to content scanners (declare, spark-table)
  * - `as` controls rendering (none, codeblock, md-table, md-card, md-dice)
  * - `id` is used for cross-references (file paths)
+ *
+ * Attribute parsing itself lives in `src/markdown/block-attrs.ts` so render
+ * extensions can share the same syntax.
  */
 
-// ---------------------------------------------------------------------------
-// Types
-// ---------------------------------------------------------------------------
-
-export interface BlockAttrs {
-  lang: string;
-  id?: string;
-  role?: string;
-  as?: string;
-  /** Any other attributes not in the standard set */
-  extra: Record<string, string>;
-}
+export { parseBlockAttrs, type BlockAttrs } from "../../markdown/block-attrs";
 
 // ---------------------------------------------------------------------------
 // Regex
@@ -29,23 +21,6 @@ export interface BlockAttrs {
 /** Matches fenced code blocks with an info string (at least one attr). */
 export const FENCED_BLOCK_RE = /^```(\w*)\s+(\S.*?)\s*\n([\s\S]*?)```\s*$/gm;
 
-// ---------------------------------------------------------------------------
-// Attribute parsing
-// ---------------------------------------------------------------------------
-
-/** Parse key="value" and key=value pairs from an attribute string. */
-export function parseBlockAttrs(info: string): BlockAttrs {
-  const attrs: Record<string, string> = {};
-  const re = /(\w+)\s*=\s*("[^"]*"|\S+)/g;
-  let m: RegExpExecArray | null;
-  while ((m = re.exec(info)) !== null) {
-    attrs[m[1]] = m[2].replace(/^"|"$/g, "");
-  }
-
-  const { lang, id, role, as, ...extra } = attrs;
-  return { lang: lang || "", id, role, as, extra };
-}
-
 // ---------------------------------------------------------------------------
 // as resolution
 // ---------------------------------------------------------------------------