Pin fresh task worktree creation to the resolved integration branch when no explicit executionStartBranch is present, so ambient root checkout state cannot leak sibling task commits into new branches.
Use task baseCommitSha for merge-finalization branch proof when available, allowing already-landed mergeConfirmed tasks to finalize even if historical branch ancestry contains foreign commits.
Fusion-Task-Id: FN-7360
88bcbce0fe