fix(kb-ui): make the object reader readable — reflow, window, jump-to

The reader dumped the whole server slice verbatim: a ~445k-char doc rendered
as a 16,558px wall of one-source-line-per-line ragged text, and the outline
panel showed 8 blank rows (the API's sections carry heading:null — they're
mechanical 60k-char chunks, not headings).

- Reflow: off the citation path, parse the extracted markdown/PDF text into
  real blocks — drop form-feeds, split on blank lines, join soft-wrapped
  lines into paragraphs, lift markdown headings + multi-line bullet lists.
  Cap prose width at 68ch. The citation-highlight path still renders the raw
  slice verbatim so character offsets stay exact.
- Window every load: initial 8k chars, "Read more" +12k, section jump loads a
  bounded window from the section's start (server honours start/end precisely).
  Object height 16,558 → ~5,315px; Read more/citations verified.
- Outline: blank heading:null rows now render as "Part N" jump points and the
  panel is titled "Jump to" (vs "Outline") when there are no real headings;
  aria-current on the active row.

Verified live on dev-knowledge.sky-ai.com.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components-object.tsx

@@ -28,6 +28,16 @@ import {
   isImageMime,
 } from "./_internal";
 
+// The reader loads a bounded window and reveals more on demand — a long
+// document (this one is ~445k chars) must never render as a single wall.
+const INITIAL_CHARS = 8000;
+const MORE_CHARS = 12000;
+
+/** A section's display label — real heading, else a mechanical "Part N". */
+function sectionLabel(s: OutlineSection, index: number): string {
+  return s.heading?.trim() || `Part ${index + 1}`;
+}
+
 // ---- ObjectList -----------------------------------------------------------
 
 export interface ObjectListProps {
@@ -222,20 +232,21 @@ export const OutlineNav: FC<{
 }> = ({ sections, activeId, onSelect, className }) => {
   if (sections.length === 0) return null;
   return (
-    <nav className={cn("flex flex-col gap-0.5", className)} aria-label="Document outline">
+    <nav className={cn("flex flex-col gap-0.5", className)} aria-label="Document sections">
-      {sections.map((s) => (
+      {sections.map((s, i) => (
         <button
           key={s.id}
           type="button"
           data-action="knowledge-outline-section"
           onClick={() => onSelect?.(s)}
+          aria-current={activeId === s.id ? "true" : undefined}
           className={cn(
             "truncate rounded-md px-2 py-1 text-left text-sm transition hover:bg-muted",
             s.level > 1 && "pl-4 text-xs",
             activeId === s.id ? "bg-muted font-medium text-foreground" : "text-muted-foreground",
           )}
         >
-          {s.heading}
+          {sectionLabel(s, i)}
         </button>
       ))}
     </nav>
@@ -282,17 +293,21 @@ export const TextReader: FC<TextReaderProps> = ({ outline, readText, highlight,
     [readText],
   );
 
-  // Initial + reactive loads: an explicit outline selection wins (so clicking a
+  // Initial + reactive loads, always bounded to a window so a long document
-  // section works even on a citation-opened view), then the highlight span,
+  // never renders as one wall. An explicit section selection wins (jump to its
-  // else the head of the document.
+  // start), then a citation highlight span, else the head of the document.
   useEffect(() => {
     if (activeSection) {
-      void load({ section: activeSection });
+      const sec = outline.outline.find((s) => s.id === activeSection);
+      void load(
+        sec
+          ? { start: sec.start, end: Math.min(sec.end, sec.start + INITIAL_CHARS) }
+          : { section: activeSection },
+      );
     } else if (highlight) {
-      const sec = outline.outline.find((s) => highlight.start >= s.start && highlight.end <= s.end);
+      void load({ start: Math.max(0, highlight.start - 400), end: highlight.end + 1200 });
-      void load(sec ? { section: sec.id } : { start: Math.max(0, highlight.start - 200), end: highlight.end + 200 });
     } else {
-      void load();
+      void load({ start: 0, end: INITIAL_CHARS });
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [highlight?.start, highlight?.end, activeSection, outline.object_id]);
@@ -305,7 +320,7 @@ export const TextReader: FC<TextReaderProps> = ({ outline, readText, highlight,
     if (loadingMore || !slice?.range) return;
     setLoadingMore(true);
     try {
-      const next = await readText({ start: slice.range.end });
+      const next = await readText({ start: slice.range.end, end: slice.range.end + MORE_CHARS });
       setSlice((prev) =>
         prev && prev.range && next.range
           ? { ...next, text: (prev.text ?? "") + (next.text ?? ""), range: { start: prev.range.start, end: next.range.end } }
@@ -346,8 +361,15 @@ export const TextReader: FC<TextReaderProps> = ({ outline, readText, highlight,
 
   return (
     <div className={className}>
-      <article className="whitespace-pre-wrap break-words text-sm leading-relaxed text-foreground">
+      <article className="max-w-[68ch] break-words text-sm leading-relaxed text-foreground">
-        {renderWithHighlight(slice, highlight, markRef)}
+        {highlight ? (
+          // Citation landing: exact character offsets must be preserved so the
+          // mark lands on the cited span, so render the raw slice verbatim.
+          <div className="whitespace-pre-wrap break-words">{renderWithHighlight(slice, highlight, markRef)}</div>
+        ) : (
+          // Reading: reflow the soft-wrapped source into real paragraphs.
+          renderReadable(slice.text ?? "")
+        )}
       </article>
       {error && <p className="mt-2 text-xs text-destructive">{error}</p>}
       {canReadMore && (
@@ -366,6 +388,53 @@ export const TextReader: FC<TextReaderProps> = ({ outline, readText, highlight,
   );
 };
 
+// Reflow extracted text (markdown / PDF dumps) into readable blocks. The source
+// hard-wraps prose with single newlines and separates paragraphs with blank
+// lines; rendered verbatim that's a ragged one-line-per-line wall. Here: drop
+// page-break form-feeds, split on blank lines, join soft-wrapped lines within a
+// block, and lift markdown headings / bullets. Offset-independent, so it's only
+// used off the citation path (which needs verbatim offsets).
+const HEADING_RE = /^(#{1,6})\s+(.*)$/;
+const BULLET_RE = /^\s*([-*•]|\d+[.)])\s+/;
+
+function renderReadable(raw: string): ReactNode {
+  const text = raw.replace(/\r\n?/g, "\n").replace(/\f/g, "\n\n");
+  const blocks = text.split(/\n[ \t]*\n+/);
+  const out: ReactNode[] = [];
+  blocks.forEach((block, bi) => {
+    const lines = block.split("\n").map((l) => l.trimEnd()).filter((l) => l.trim() !== "");
+    if (lines.length === 0) return;
+
+    const h = lines.length === 1 ? HEADING_RE.exec(lines[0]) : null;
+    if (h) {
+      const level = h[1].length;
+      out.push(
+        <p key={bi} className={cn("mb-1 mt-4 font-semibold text-foreground first:mt-0", level <= 2 ? "text-base" : "text-sm")}>
+          {h[2]}
+        </p>,
+      );
+      return;
+    }
+
+    // A real list needs 2+ marker lines; a lone "1. Introduction" is a heading
+    // or TOC line, not a one-item bullet.
+    if (lines.length >= 2 && lines.every((l) => BULLET_RE.test(l))) {
+      out.push(
+        <ul key={bi} className="my-2 list-disc space-y-1 pl-5">
+          {lines.map((l, li) => (
+            <li key={li}>{l.replace(BULLET_RE, "")}</li>
+          ))}
+        </ul>,
+      );
+      return;
+    }
+
+    const para = lines.join(" ").replace(/[ \t]+/g, " ").trim();
+    if (para) out.push(<p key={bi} className="my-2 first:mt-0">{para}</p>);
+  });
+  return out.length > 0 ? out : raw;
+}
+
 function renderWithHighlight(
   slice: TextSlice,
   highlight: { start: number; end: number } | undefined,
@@ -527,7 +596,9 @@ export const ObjectViewer: FC<ObjectViewerProps> = ({
         <aside className="flex flex-col gap-4">
           {outline.outline.length > 0 && (
             <div className="rounded-xl border border-border bg-card p-3">
-              <h3 className="mb-2 px-2 text-xs font-semibold uppercase tracking-wide text-muted-foreground">Outline</h3>
+              <h3 className="mb-2 px-2 text-xs font-semibold uppercase tracking-wide text-muted-foreground">
+                {outline.outline.some((s) => s.heading?.trim()) ? "Outline" : "Jump to"}
+              </h3>
               <OutlineNav sections={outline.outline} activeId={activeSection} onSelect={(s) => setActiveSection(s.id)} />
             </div>
           )}