Page-split now creates independent sessions (no parent_session_id),
parent marked as status='split' and hidden from list. Navigation uses
useSearchParams for URL-based step tracking (browser back/forward works).
page.tsx reduced from 684 to 443 lines via usePipelineNavigation hook.
Box sub-sessions (column detection) remain unchanged.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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