The session has autoflush off, so recompute_dirty's query read the last-committed
state, not the current request's pending item/order edits — so the first reorder
after a sync compared against itself and missed dirty, and only the next edit showed
it. Flush pending changes before computing the current fingerprint. Verified: a swap
now flips dirty immediately, and reverting to the original clears it.
7b8f835226