v0.12.255 — img2img abort guards + result-asset download cancellation
Fixed — img2img no longer misreports a client cancel as "Invalid request"
The /v1/images/image2image parse path downloads source/mask URLs with the client-abort signal (v0.12.252), so a caller hanging up mid-download rejects that fetch with an AbortError — which the parse catch then misclassified as invalid input and answered with a 400 on the dead socket. The catch now returns silently when clientAbort.signal.aborted is set, and the paid upstream is never contacted. Covered by a new case in src/proxy.img2img-abort.test.ts (download socket observes the abort, no response is written, zero upstream hits). Closes #277.
Also landed the remainder of PR #276 (same lineage): the three post-payment result-asset downloads — generations and img2img result images, video clips — now carry clientAbort.signal so a hung download is cancelled when the client leaves instead of running to the 5-minute fetch ceiling, and the chat-path /imagegen outer catch gained the same silent-return abort guard its /img2img sibling got in v0.12.253.
