Resolves 4 merge conflicts: Toolbar.tsx (2), Canvas.a11y.test.tsx (1),
Canvas.pan-to-node.test.tsx (1). All conflicts were additive — PR adds
selectedNodeId/setPanelTab selectors and the Audit toolbar button; main
didn't have them. Took PR additions throughout.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>