feat(viewer): show document summary together with the original (TODO.md L5)

frontend/assets/document.js

@@ -12,7 +12,13 @@
  *                         in a ≤46rem centered column;
  *       • any other     → the raw content as a text node inside
  *                         <pre class="doc-raw"> (mono, horizontal
- *                         scroll).
+ *                         scroll);
+ *       • doc.summary non-empty (phase 36 — phase 30 summaries exist
+ *                         only on non-markdown docs) → a labeled
+ *                         .doc-summary section ABOVE the content;
+ *                         null / empty / whitespace renders nothing, so
+ *                         markdown docs and fail-soft rows are
+ *                         byte-for-byte unchanged.
  *
  *  2. The /document.html page itself: reads `source`/`path` query
  *     params, fetches the stateless content endpoint
@@ -40,6 +46,11 @@
  * around the page block below). Importing renderDocument elsewhere has
  * no side effects: no back-link resolution, no whoami, no content
  * fetch, no New Chat binding.
+ *
+ * Phase 36: the renderer owns the optional summary panel — a non-empty
+ * doc.summary renders as a labeled .doc-summary section above the
+ * original content on BOTH surfaces (page + modal) through this one
+ * core; the summary text is a text node (XSS contract unchanged).
  */
 
 import { fetchIsAdmin, initSharedHeader } from "./header.js";
@@ -66,10 +77,13 @@ function metaBadge(cls, text) {
 /* ---------- shared renderer (phase 26, task 02) ----------
  * Populates the three elements every render surface provides: a title,
  * a .doc-meta badge row (source · format · mono path · indexed ·
- * chunks), and a content container — .doc-md for md/markdown (the
- * shared escape-first renderer), <pre class="doc-raw"> otherwise. The
- * XSS contract: innerHTML only through renderMarkdown; every
- * document-derived string is a text node. */
+ * chunks), and a content container — an optional .doc-summary section
+ * first (phase 36: only when doc.summary is non-empty — markdown docs
+ * and fail-soft rows carry none, so they render exactly as before),
+ * then .doc-md for md/markdown (the shared escape-first renderer),
+ * <pre class="doc-raw"> otherwise. The XSS contract: innerHTML only
+ * through renderMarkdown; every document-derived string (summary text
+ * included) is a text node. */
 export function renderDocument(doc, { titleEl, metaEl, contentEl }) {
   titleEl.textContent = doc.title;
   // Phase 34 task 04: the titlebar title ellipsizes — the full title
@@ -88,6 +102,24 @@ export function renderDocument(doc, { titleEl, metaEl, contentEl }) {
   );
 
   contentEl.replaceChildren();
+  // Phase 36: the summary panel — labeled section ABOVE the original
+  // content, on BOTH surfaces (page + modal) through this one core.
+  // Only a non-empty summary renders: markdown docs carry none (phase
+  // 30) and the fail-soft path leaves summary NULL, so both are
+  // byte-for-byte unchanged here.
+  if (doc.summary && doc.summary.trim() !== "") {
+    const section = document.createElement("section");
+    section.className = "doc-summary";
+    section.setAttribute("aria-label", "Summary");
+    const title = document.createElement("h2");
+    title.className = "doc-summary-title";
+    title.textContent = "Summary";
+    const body = document.createElement("p");
+    body.className = "doc-summary-text";
+    body.textContent = doc.summary; // text node — XSS contract unchanged
+    section.append(title, body);
+    contentEl.appendChild(section);
+  }
   if (doc.format === "md" || doc.format === "markdown") {
     const wrap = document.createElement("div");
     wrap.className = "doc-md";