Controller-ruled small fixes accumulated from T3/T4 reviews:
1. routes_media.go: multipart Content-Type check is now an exact
mediaType != "multipart/form-data" comparison (HasPrefix admitted
"multipart/form-datax"); a malformed-tail multipart body (fails to
parse at all) now reports "malformed multipart body", distinct from
"model is required" (a body that parses fine but carries no model
part) and "duplicate model field".
2. provider_openai.go: audioTranscription's doc comment no longer claims
the body is always "replayed unchanged"/the boundary always
"verbatim" — it now reflects the rewrite path routes_media.go
already takes for an aliased model id.
3. rewriteMultipartModel: buf.Grow(len(body)+512) up front, avoiding
repeated reallocate-and-copy growth while rebuilding an aliased
multipart body.
4. limits.go currentUsage: guards len(vals) == len(keys) before indexing
storeGetMulti's result, so a non-conforming counterStore's short slice
reports storeDown instead of panicking.
5. admin.go dashboard JS: the 5s poll no longer wipes an existing
auth-error message when no key is stored (only a successful load or a
new submission clears it now); clearStoredKey on a 401/403 now only
fires when the failing request's own key still matches what's
currently stored, guarding against a late response for a key the user
has since replaced.
6. Spec §4's duplicated /admin/api/overview bullet and the
nosniff/no-store sentence's placement were already fixed upstream
(docs/superpowers/specs/2026-08-20-llmgateway-v02-design.md, commit
c02010d) — verified identical, nothing further to commit here.
7. Added TestAdmin_JSONSecurityHeaders (nosniff/no-store/CSP on both
admin JSON APIs) and TestHandleAudioTranscriptions_MalformedTail_400
(covers fix 1's new malformed-body branch).
go test ./... -count=1 -race, gofmt, vet, make yaegi-check, golangci-lint
(incl. gosec) all pass.
lukaszraczylo