feat: miller column browser, offline cache, search, breadcrumbs

- Dynamic miller column sizing with flexbox layout
- Root column (160px), middle slices (48px), active column (flex)
- Auto-scroll browser to rightmost column on navigation
- Offline indicator UI and IndexedDB cache integration
- /api/documents endpoint for client-side document caching
- Breadcrumb navigation in document content area
- FTS5 search with SQLite virtual table
- Client-side Mermaid and KaTeX rendering via CDN
- Deep sample content (advanced-topics/raft-deep-dive)
- Border removal (only search button keeps radius)
- Full viewport layout with proper borders between sidebar/content

apps/server/internal/docs/repository.go

@@ -271,6 +271,47 @@ func (r *Repository) GetAttachment(ctx context.Context, hash string) (*Attachmen
 	return &record, nil
 }
 
+type SearchResult struct {
+	Path  string `json:"path"`
+	Title string `json:"title"`
+}
+
+func (r *Repository) SearchDocuments(ctx context.Context, query string) ([]SearchResult, error) {
+	rows, err := r.db.QueryContext(ctx, `
+		SELECT d.path, d.title
+		FROM document_search ds
+		JOIN documents d ON d.rowid = ds.rowid
+		WHERE document_search MATCH ?
+		ORDER BY rank
+		LIMIT 50
+	`, query)
+	if err != nil {
+		return nil, fmt.Errorf("search documents: %w", err)
+	}
+	defer rows.Close()
+
+	var results []SearchResult
+	for rows.Next() {
+		var result SearchResult
+		if err := rows.Scan(&result.Path, &result.Title); err != nil {
+			return nil, fmt.Errorf("scan search result: %w", err)
+		}
+		results = append(results, result)
+	}
+
+	return results, rows.Err()
+}
+
+func (r *Repository) UpdateSearchContent(ctx context.Context, path string, content string) error {
+	if _, err := r.db.ExecContext(ctx, `
+		UPDATE document_search SET content = ?
+		WHERE rowid = (SELECT rowid FROM documents WHERE path = ?)
+	`, content, path); err != nil {
+		return fmt.Errorf("update search content: %w", err)
+	}
+	return nil
+}
+
 func (r *Repository) Ping(ctx context.Context) error {
 	return r.db.PingContext(ctx)
 }