Two follow-ups from code review of c5f0449:
1. In MV3 the SW can be killed mid-message; sendMessage then resolves
to undefined. Add `(!resp || !resp.ok)` guards at 4 call sites
(fetchThumbUrl, settings fetch, upload, download) plus optional
chaining on error accessors.
2. JSDoc on wireAttachmentsDisclosure documents the "call once per DOM
instance" contract — Task 8's re-wire pattern works because it
replaces outerHTML before re-attaching, destroying old listeners
via GC.
Module-level objectUrlRegistry concern (concurrent disclosure
instances) deferred — current popup architecture renders one item at
a time, so the issue doesn't manifest today.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
dcb1590391