feat(markdown): extract MITRE citations into collapsible sources section

(Citation: ...) patterns are stripped from body text, replaced with
Unicode superscript numbers (¹²³), and shown in a compact "Sources"
section below — collapsed when there are more than 3, expanded otherwise.
Deduplication ensures the same citation reference appears only once.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/MarkdownText.tsx

@@ -1,26 +1,63 @@
 /**
  * MarkdownText — renders a markdown string as styled HTML.
  *
- * Uses react-markdown + remark-gfm (tables, strikethrough, etc.).
- * External links always open in a new tab with rel="noopener noreferrer".
+ * Features:
+ * - react-markdown + remark-gfm (tables, strikethrough, etc.)
+ * - External links open in a new tab.
+ * - MITRE (Citation: ...) patterns are extracted from the body text,
+ *   replaced with superscript numbers ¹²³, and shown as a compact
+ *   collapsible "Sources" section below.
  *
  * Usage:
  *   <MarkdownText content={technique.description} />
  *   <MarkdownText content={test.red_summary} className="text-sm text-gray-400" />
  */
 
+import { useState } from "react";
 import ReactMarkdown from "react-markdown";
 import remarkGfm from "remark-gfm";
 import type { Components } from "react-markdown";
+import { ChevronDown, ChevronUp, BookOpen } from "lucide-react";
 
-interface MarkdownTextProps {
-  content: string | null | undefined;
-  /** Extra classes on the wrapper div */
-  className?: string;
+/* ── Citation pre-processing ──────────────────────────────────────── */
+
+const CITATION_RE = /\s*\(Citation:\s*([^)]+)\)/g;
+
+const SUPERSCRIPTS = "⁰¹²³⁴⁵⁶⁷⁸⁹";
+
+function toSuperscript(n: number): string {
+  return String(n)
+    .split("")
+    .map((d) => SUPERSCRIPTS[parseInt(d)] ?? d)
+    .join("");
 }
 
-const components: Components = {
-  // Links: always open external URLs in a new tab
+interface ProcessedContent {
+  /** Text with (Citation: …) replaced by ¹²³ superscript numbers */
+  text: string;
+  /** Ordered list of unique citation strings */
+  citations: string[];
+}
+
+function processCitations(raw: string): ProcessedContent {
+  const citations: string[] = [];
+
+  const text = raw.replace(CITATION_RE, (_, cite: string) => {
+    const trimmed = cite.trim();
+    let idx = citations.indexOf(trimmed);
+    if (idx === -1) {
+      citations.push(trimmed);
+      idx = citations.length - 1;
+    }
+    return toSuperscript(idx + 1);
+  });
+
+  return { text: text.trim(), citations };
+}
+
+/* ── ReactMarkdown component overrides ───────────────────────────── */
+
+const mdComponents: Components = {
   a: ({ href, children, ...props }) => (
     <a
       href={href}
@@ -32,19 +69,13 @@ const components: Components = {
       {children}
     </a>
   ),
-  // Paragraphs: keep existing text colour, add spacing
   p: ({ children }) => (
     <p className="mb-2 last:mb-0 leading-relaxed">{children}</p>
   ),
-  // Bold
   strong: ({ children }) => (
     <strong className="font-semibold text-gray-100">{children}</strong>
   ),
-  // Italic
-  em: ({ children }) => (
-    <em className="italic text-gray-300">{children}</em>
-  ),
-  // Inline code
+  em: ({ children }) => <em className="italic text-gray-300">{children}</em>,
   code: ({ children, className }) => {
     const isBlock = className?.startsWith("language-");
     if (isBlock) {
@@ -60,22 +91,18 @@ const components: Components = {
       </code>
     );
   },
-  // Code blocks
   pre: ({ children }) => (
     <pre className="my-2 overflow-x-auto rounded-md bg-gray-800 p-3 text-xs">
       {children}
     </pre>
   ),
-  // Unordered lists
   ul: ({ children }) => (
     <ul className="mb-2 list-disc pl-5 space-y-0.5">{children}</ul>
   ),
-  // Ordered lists
   ol: ({ children }) => (
     <ol className="mb-2 list-decimal pl-5 space-y-0.5">{children}</ol>
   ),
   li: ({ children }) => <li className="leading-relaxed">{children}</li>,
-  // Headings (rarely appear in descriptions but handle them gracefully)
   h1: ({ children }) => (
     <h1 className="mb-2 text-base font-semibold text-white">{children}</h1>
   ),
@@ -85,24 +112,72 @@ const components: Components = {
   h3: ({ children }) => (
     <h3 className="mb-1 text-sm font-medium text-gray-200">{children}</h3>
   ),
-  // Blockquotes
   blockquote: ({ children }) => (
     <blockquote className="my-2 border-l-2 border-cyan-500/40 pl-3 text-gray-400 italic">
       {children}
     </blockquote>
   ),
-  // Horizontal rule
   hr: () => <hr className="my-3 border-gray-700" />,
 };
 
+/* ── Citations footer sub-component ─────────────────────────────── */
+
+function CitationsFooter({ citations }: { citations: string[] }) {
+  // Auto-expand if few citations; collapse for many
+  const [open, setOpen] = useState(citations.length <= 3);
+
+  return (
+    <div className="mt-3 border-t border-gray-800 pt-2">
+      <button
+        onClick={() => setOpen((o) => !o)}
+        className="flex items-center gap-1.5 text-[11px] text-gray-500 hover:text-gray-400 transition-colors select-none"
+      >
+        <BookOpen className="h-3 w-3" />
+        <span>
+          {citations.length} source{citations.length !== 1 ? "s" : ""}
+        </span>
+        {open ? (
+          <ChevronUp className="h-3 w-3" />
+        ) : (
+          <ChevronDown className="h-3 w-3" />
+        )}
+      </button>
+
+      {open && (
+        <ol className="mt-1.5 space-y-0.5 list-none">
+          {citations.map((cite, i) => (
+            <li key={i} className="flex items-baseline gap-1.5 text-[11px] text-gray-500">
+              <span className="shrink-0 text-gray-600 select-none">
+                {toSuperscript(i + 1)}
+              </span>
+              <span className="font-mono">{cite}</span>
+            </li>
+          ))}
+        </ol>
+      )}
+    </div>
+  );
+}
+
+/* ── Main component ──────────────────────────────────────────────── */
+
+interface MarkdownTextProps {
+  content: string | null | undefined;
+  /** Extra classes on the wrapper div */
+  className?: string;
+}
+
 export default function MarkdownText({ content, className }: MarkdownTextProps) {
   if (!content) return null;
 
+  const { text, citations } = processCitations(content);
+
   return (
     <div className={className}>
-      <ReactMarkdown remarkPlugins={[remarkGfm]} components={components}>
-        {content}
+      <ReactMarkdown remarkPlugins={[remarkGfm]} components={mdComponents}>
+        {text}
       </ReactMarkdown>
+      {citations.length > 0 && <CitationsFooter citations={citations} />}
     </div>
   );
 }