Fix stale cache after move operation

[chm-diederichs]

• WriteBatch serialization renumbers pointer objects in place (k.seq/k.offset = ), and those objects are shared into older nodes' delta lists through CompressedArray.commit(). The decoder rebuilds nodes purely from their own block's delta list, so the in-memory delta is what gets serialized. The design assumption is that an old node object is never re-serialized after a newer flush and autobee's undo (move() to an older length) violates exactly that: the node cache hands back the old root object whose delta pointers now reference the newer, just-abandoned block, and the post-undo re-apply flushes garbage references to disk.

• commit()'s slice(0, -this.updates) with updates === 0 (slice(0, -0) = slice(0, 0)) wipes the live node's delta

claude opus 4.8