feat: media expansion surfaces — edit mask, upscale, background removal, interpolation, diarization, meshgen (ADR-0020)

- imagegen.EditRequest.Mask -> sd-server img2img inpainting (white=repaint)
- imagegen.Upscaler + BackgroundRemover, videogen.Interpolator,
  audio.DiarizationModel: new optional provider-minted surfaces
- NEW meshgen leaf package (image->3D, glb/stl/obj)
- provider/llamaswap: all five via the /upstream/<model>/<path> passthrough
  (upstreamPath helper, shared one-file multipart builder); binary success
  bodies validated (non-image, non-video, JSON-mesh rejection); diarization
  pins output=json (vtt/srt drop speaker labels)

Co-Authored-By: Claude Fable 5 <[email protected]>

provider/llamaswap/diarize.go

@@ -0,0 +1,122 @@
+// diarize.go implements audio.DiarizationProvider against a
+// whisper-asr-webservice upstream (WhisperX engine) reached through
+// llama-swap's /upstream passthrough (ADR-0020):
+//
+//	POST /upstream/<id>/asr?output=json&diarize=true[&language&min_speakers&max_speakers]
+//
+// output=json is load-bearing: the vtt/srt output formats DROP the speaker
+// labels; only the json shape carries per-segment `speaker` fields.
+package llamaswap
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"gitea.stevedudenhoeffer.com/steve/majordomo/audio"
+	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
+)
+
+// DiarizationModel implements audio.DiarizationProvider. The id selects
+// which upstream llama-swap loads (the pyannote-equipped WhisperX sidecar,
+// not the plain whisper.cpp model).
+func (p *Provider) DiarizationModel(id string, opts ...audio.DiarizationModelOption) (audio.DiarizationModel, error) {
+	if err := p.requireBaseURL(); err != nil {
+		return nil, err
+	}
+	_ = audio.ApplyDiarizationModelOptions(opts)
+	return &diarizationModel{p: p, id: id}, nil
+}
+
+type diarizationModel struct {
+	p  *Provider
+	id string
+}
+
+// asrResponse is whisper-asr-webservice's output=json shape (the subset this
+// package relies on; per-word entries are ignored — segment granularity is
+// the contract).
+type asrResponse struct {
+	Text     string `json:"text"`
+	Language string `json:"language"`
+	Segments []struct {
+		Start   float64 `json:"start"`
+		End     float64 `json:"end"`
+		Text    string  `json:"text"`
+		Speaker string  `json:"speaker"`
+	} `json:"segments"`
+}
+
+// Diarize implements audio.DiarizationModel.
+func (m *diarizationModel) Diarize(ctx context.Context, req audio.DiarizationRequest, opts ...audio.DiarizationOption) (*audio.DiarizationResult, error) {
+	req = req.Apply(opts...)
+	if len(req.Audio) == 0 {
+		return nil, fmt.Errorf("%w: diarization requires audio bytes", llm.ErrUnsupported)
+	}
+	if req.MinSpeakers < 0 || req.MaxSpeakers < 0 ||
+		(req.MaxSpeakers > 0 && req.MinSpeakers > req.MaxSpeakers) {
+		return nil, fmt.Errorf("%w: invalid speaker bounds [%d,%d]", llm.ErrUnsupported, req.MinSpeakers, req.MaxSpeakers)
+	}
+
+	q := url.Values{}
+	q.Set("output", "json")
+	q.Set("diarize", "true")
+	if req.Language != "" {
+		q.Set("language", req.Language)
+	}
+	if req.MinSpeakers > 0 {
+		q.Set("min_speakers", strconv.Itoa(req.MinSpeakers))
+	}
+	if req.MaxSpeakers > 0 {
+		q.Set("max_speakers", strconv.Itoa(req.MaxSpeakers))
+	}
+	path, err := upstreamPath(m.id, "/asr?"+q.Encode())
+	if err != nil {
+		return nil, err
+	}
+
+	body, contentType, err := buildMultipart("build diarization form",
+		filePart{field: "audio_file", filename: diarizationFilename(req), data: req.Audio},
+		nil)
+	if err != nil {
+		return nil, err
+	}
+	raw, _, err := m.p.doRaw(ctx, http.MethodPost, path, m.id, contentType, body, maxResponseBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	var out asrResponse
+	if err := json.Unmarshal(raw, &out); err != nil {
+		return nil, fmt.Errorf("llama-swap: decode diarization response: %w", err)
+	}
+	res := &audio.DiarizationResult{
+		Text:     out.Text,
+		Language: out.Language,
+		Raw:      json.RawMessage(raw),
+	}
+	for _, s := range out.Segments {
+		res.Segments = append(res.Segments, audio.DiarizationSegment{
+			Start:   s.Start,
+			End:     s.End,
+			Speaker: s.Speaker,
+			Text:    s.Text,
+		})
+	}
+	if len(res.Segments) == 0 && res.Text == "" {
+		return nil, &llm.APIError{Provider: m.p.name, Model: m.id, Message: "diarization response contained no transcript"}
+	}
+	return res, nil
+}
+
+// diarizationFilename mirrors transcriptionFilename for the diarization
+// request shape (same untrusted-metadata sanitization rules).
+func diarizationFilename(req audio.DiarizationRequest) string {
+	return transcriptionFilename(audio.TranscriptionRequest{
+		Filename: req.Filename,
+		MIME:     req.MIME,
+	})
+}