fix: review findings — clone-route audio sniffing, zip caps, filename sanitization, WAV response caps

- speakWithReference now validates the response IS audio via the same
  audioResultMIME sniff the sfx/enhance surfaces use — a 2xx JSON soft
  error or HTML proxy page was previously wrapped up as audio/wav bytes.
- audioResultMIME moves to audio.go (next to speechMIME; it was defined
  in sfx.go but shared by enhance/clone) and learns the Ogg container
  normalization (application/ogg -> audio/ogg).
- Stems zip unpack gains entry-count (16) and total-decompressed (1GB)
  caps on top of the existing per-entry cap — the per-entry bound alone
  still let a many-entry bomb multiply up.
- sanitizeFilename drops NUL and both path separators too, so upload
  metadata can never smuggle directory structure to a file-writing shim.
- New maxAudioResponseBytes (256MB) for bodies that ARE one audio clip
  (clone, enhance, sfx): a long WAV legitimately passes the 64MB JSON
  cap.
- speakWithReference local renamed path -> upPath (naming parity with
  stems/enhance).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01WWCQcYStWXBYUy5sZWnbLT

provider/llamaswap/sfx.go

@@ -84,7 +84,7 @@ func (m *sfxModel) Generate(ctx context.Context, req musicgen.Request, opts ...m
 	if err != nil {
 		return nil, fmt.Errorf("llama-swap: encode sfx request: %w", err)
 	}
-	raw, contentType, err := m.p.doRaw(ctx, http.MethodPost, path, m.id, "application/json", bytes.NewReader(encoded), maxResponseBytes)
+	raw, contentType, err := m.p.doRaw(ctx, http.MethodPost, path, m.id, "application/json", bytes.NewReader(encoded), maxAudioResponseBytes)
 	if err != nil {
 		return nil, err
 	}
@@ -98,21 +98,3 @@ func (m *sfxModel) Generate(ctx context.Context, req musicgen.Request, opts ...m
 	}
 	return &musicgen.Result{Audio: musicgen.Audio{Data: raw, MIME: mimeType}}, nil
 }
-
-// audioResultMIME resolves an audio body's MIME type: the response
-// Content-Type when it is a concrete audio type, else content sniffing
-// (RIFF/WAVE and friends), else "" — the caller treats undetectable as an
-// upstream error, mirroring videoMIME. Sniffed "audio/wave" is normalized
-// to the conventional "audio/wav".
-func audioResultMIME(contentType string, data []byte) string {
-	if mt := mimeFromContentType(contentType, "audio/"); mt != "" {
-		return mt
-	}
-	if mt := http.DetectContentType(data); strings.HasPrefix(mt, "audio/") {
-		if mt == "audio/wave" {
-			return "audio/wav"
-		}
-		return mt
-	}
-	return ""
-}