Add comprehensive logging to BricksRenderer for DevPanel visibility:
1. Unknown widgettypes: WARN log with full JSON dump in DevPanel Logs tab.
Also shows [? WidgetType] orange placeholder on screen when no subwidgets.
2. Placeholder widgets (Html, MarkdownViewer, etc.): INFO log with widget summary.
3. urlwidget load failures: ERROR log with full widget JSON and error message.
4. widgetSummary(): compact one-line summary (type, id, options keys, counts).
5. widgetJsonDump(): pretty-printed JSON for deep inspection in DevPanel.
Previously: unknown widgets silently fell through to subwidget rendering.
Now: every unrecognized widget is visible in DevPanel with full context.
yumoqing
fe6261598b