fix: show() reparented lists in side-by-side so they lay out

QTabWidget hides its non-current pages. Pinning a tab that wasn't the active
one reparented a hidden QListWidget into the split panel, where it stayed
hidden — the layout collapsed it, overlapping the header in the middle with
an empty/black list. setVisible(True) after reparenting fixes the panes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

main.py

@@ -4579,6 +4579,9 @@ class MainWindow(QMainWindow):
                     pl.addWidget(header)
                     pw.setMinimumWidth(60)
                     pl.addWidget(pw, 1)
+                    # QTabWidget hides non-current pages; reparented pinned lists
+                    # stay hidden and break the layout unless re-shown.
+                    pw.setVisible(True)
                     pw._rebuild()
                     splitter.addWidget(panel)
                 splitter.setSizes([1000] * len(pinned))