Sequential Updates resolve to the second to last Update

[ayumi]

Repro:

• In browser-laptop, creating a bookmark and renaming it is 2 Updates.
• The next Sync interval, Sync resolves both Updates against the newest browser state:
  • Update 1 differs, so it's kept.
  • Update 2 is the same, so it's discarded.

Expected behavior:

• When a resolve batch contains records with the same objectId, it should discard stale data.

Bonus:

• browser-laptop should emit Create then Update, which would resolve to no op.