Spec Kitty

Mission Run: Finalize re-pins an orphaned planning_commit_sha after a rebase

Stop finalize-tasks from wedging a mission when an upstream rebase orphans the pinned planning commit.

When a mission branch is rebased onto a moved base mid-mission, the planning commit is rewritten to a new SHA and the one recorded in lanes.json is orphaned. Today finalize-tasks silently preserves that dead SHA (or refuses to re-point it), so lane allocation and dependency-lane auto-merge fail against a commit that is no longer on the branch — a P0 wedge on the supported full-mission drive whose only escape is hand-editing lanes.json. This mission makes finalize detect the orphaned pin and re-pin it to the live planning commit, and makes the lane allocator name a stale pin instead of reporting a false merge conflict.