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/stems_sfx_enhance_test.go

@@ -6,8 +6,10 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"gitea.stevedudenhoeffer.com/steve/majordomo/audio"
@@ -169,6 +171,27 @@ func TestSeparateStemsRejectsEmptyZip(t *testing.T) {
 	}
 }
 
+func TestSeparateStemsRejectsTooManyEntries(t *testing.T) {
+	entries := map[string]string{}
+	for i := 0; i <= maxStemEntries; i++ {
+		entries[fmt.Sprintf("stem%02d.wav", i)] = "X"
+	}
+	zipBody := stemsZipFixture(t, entries)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/zip")
+		_, _ = w.Write(zipBody)
+	}))
+	defer srv.Close()
+
+	p := New(WithBaseURL(srv.URL), WithHTTPClient(srv.Client()))
+	ss, _ := p.StemSeparatorModel("audioutils")
+	_, err := ss.SeparateStems(context.Background(), audio.StemSeparationRequest{Audio: []byte("SONG")})
+	var apiErr *llm.APIError
+	if !errors.As(err, &apiErr) || !strings.Contains(apiErr.Message, "entries") {
+		t.Fatalf("err = %v, want APIError for over-long stems zip", err)
+	}
+}
+
 // wavFixture is a minimal RIFF/WAVE header so http.DetectContentType sniffs
 // audio/wave.
 func wavFixture() []byte {