validateImageBuffer() never listed heif in CLI_DECODED_FORMATS, so real iPhone HEIC uploads hit Sharp's own metadata probe (its bundled libheif only supports AV1/AVIF) and got rejected before reaching the working heif-convert/heif-dec decode path already wired up downstream. Adds heif to that set, same as raw/psd/tga/bmp/etc.
Also fixes the same gap on erase-object's mask input, which validates through the same function but had no matching decode step, so a HEIC mask reached an unguarded sharp() call and came back as a misclassified server error instead of a clean 422.
Fixes#622
Coverage 83.6 to 87.36% lines, 81.63 to 84.14% branches. Mutation testing across five packages: image-engine 85, media-engine 92, doc-engine 87, shared+enterprise 86, apps/api security and jobs slice. Runs all five lanes weekly. Fixes the silently-broken mutation CI (babel pin), a redact-pdf envelope-shape test bug, an untested enterprise license valid-signature path, and an audit test that only exercised a hand-copied reproduction. Test and config only, no product code changes beyond the babel pin and one test-only oidc export. Full suite: 16,712 pass, 0 fail.
