sync: Major UI updates from private repo (Jan 16-24)

Features synced:
- UI Panels Refactor: flexible pane system with ChatPane, NodePane,
  DimensionsPane, WorkflowsPane, ViewsPane, MapPane
- Source Content Reader: content type detection + 4 formatters
  (transcript, book, markdown, raw)
- Source Content Search: Cmd+F search in Source Reader
- Feed Layout Overhaul: LeftToolbar, SplitHandle, CollapsedRail
- Map Panel: promoted to first-class pane
- Edge policy simplification: auto-inference + direction correction

New files:
- src/components/panes/* (pane system)
- src/components/layout/CollapsedRail.tsx
- src/components/layout/LeftToolbar.tsx
- src/components/layout/SplitHandle.tsx
- src/components/focus/source/* (Source Reader + formatters)
- src/components/views/ViewsOverlay.tsx

Updated:
- ThreePanelLayout.tsx (complete refactor)
- FocusPanel.tsx (Source tab integration)
- API routes (dimensions GET, edges auto-inference)
- Database services (nodes, edges, dimensions)

Dependencies added:
- react-markdown
- remark-gfm

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/focus/source/ContentDetector.ts

@@ -0,0 +1,92 @@
+/**
+ * Content type detection for Source Reader
+ * Analyzes raw content to determine the best formatting approach
+ */
+
+export type ContentType = 'transcript' | 'book' | 'markdown' | 'article' | 'raw';
+
+// Timestamp patterns for transcript detection
+const TIMESTAMP_PATTERNS = [
+  /^\[?\d{1,2}:\d{2}(:\d{2})?\]?\s*/,   // [00:00] or [00:00:00]
+  /^\d{1,2}:\d{2}(:\d{2})?\s*[-–—]\s*/,  // 00:00 - or 00:00:00 -
+  /^\(\d{1,2}:\d{2}(:\d{2})?\)\s*/,      // (00:00) or (00:00:00)
+  /^\[\d+(\.\d+)?s\]\s*/,                // [0.1s] or [12.5s] - decimal seconds
+];
+
+// Simple book detection - look for explicit chapter markers
+// We no longer try to parse numbered sections (too unreliable)
+const BOOK_INDICATORS = [
+  /\b(CHAPTER|Chapter)\s+\d+/i,
+  /\b(Part|PART)\s+(I|II|III|IV|V|VI|VII|VIII|IX|X|\d+)\b/i,
+  /\bTable\s+of\s+Contents\b/i,
+  /\bPREFACE\b/,
+  /\bINTRODUCTION\b/,
+  /\bAPPENDIX\b/,
+];
+
+// Markdown syntax markers
+const MARKDOWN_MARKERS = [
+  /^#{1,6}\s/m,           // Headers
+  /\*\*[^*]+\*\*/,        // Bold
+  /\*[^*]+\*/,            // Italic (but not bold)
+  /^[-*+]\s/m,            // Unordered lists
+  /^\d+\.\s/m,            // Ordered lists
+  /```[\s\S]*?```/,       // Code blocks
+  /`[^`]+`/,              // Inline code
+  /\[.+\]\(.+\)/,         // Links
+];
+
+/**
+ * Detect the content type of raw source content
+ */
+export function detectContentType(content: string): ContentType {
+  if (!content || content.length < 50) return 'raw';
+
+  const lines = content.split('\n').slice(0, 50); // Check first 50 lines
+
+  // 1. Check for transcript patterns (timestamps)
+  const timestampLines = lines.filter(line =>
+    TIMESTAMP_PATTERNS.some(pattern => pattern.test(line.trim()))
+  );
+  if (timestampLines.length >= 3) return 'transcript';
+
+  // 2. Check for book indicators (explicit markers like "Chapter", "Table of Contents")
+  const bookIndicatorCount = BOOK_INDICATORS.filter(pattern => pattern.test(content)).length;
+  if (bookIndicatorCount >= 2) return 'book';
+  
+  // Also consider very long content as book-like (>20K chars)
+  if (content.length > 20000 && bookIndicatorCount >= 1) return 'book';
+
+  // 3. Check for markdown patterns
+  const markdownScore = calculateMarkdownScore(content);
+  if (markdownScore > 0.3) return 'markdown';
+
+  // 4. Check for article structure (paragraphs with clear breaks)
+  const paragraphs = content.split(/\n\n+/).filter(p => p.trim().length > 100);
+  if (paragraphs.length >= 3) return 'article';
+
+  // 5. Default to raw
+  return 'raw';
+}
+
+/**
+ * Calculate a "markdown-ness" score for content
+ * Returns a value between 0 and 1
+ */
+function calculateMarkdownScore(content: string): number {
+  const matchCount = MARKDOWN_MARKERS.filter(m => m.test(content)).length;
+  return matchCount / MARKDOWN_MARKERS.length;
+}
+
+/**
+ * Get a human-readable label for content type
+ */
+export function getContentTypeLabel(type: ContentType): string {
+  switch (type) {
+    case 'transcript': return 'Transcript';
+    case 'book': return 'Book/Chapter';
+    case 'markdown': return 'Markdown';
+    case 'article': return 'Article';
+    case 'raw': return 'Plain Text';
+  }
+}