fix(orchestration): retain nested fork history when paging

Keep the original cursor owner through ancestor traversal and preserve the history budget across empty intermediate forks. Verify exact paged history against the complete nested projection.

Finding: P01 nested lineage

Model: GPT-5.6 Sol via Codex
0c67966e9bJulius Marminge committed on 9/1/2026, 4:33:03 AMparent326442d
3 files changedLine totals unavailable