Conservative server-ordered rebase for pending offline work. Non-overlapping
literal edits are shifted across row/column insertion and deletion. Ambiguous
formula, overlapping, sheet-lifecycle, and move cases become explicit
conflicts instead of lossy guesses. This is the collaboration design gate;
no CRDT dependency is required for the supported cases.
Each local operation is written after the local operations before it, and
each remote operation after the remote operations before it. A remote
operation is therefore carried forward through the local sequence: before it
is compared with local operation k, it is moved past local operations 0..k-1.