feat: audio surfaces (TTS + transcription), imagegen.Editor, llamaswap health probe

- New leaf package `audio` (ADR-0017): SpeechModel/SpeechProvider and
  TranscriptionModel/TranscriptionProvider with imagegen conventions
  (zero value = backend default, functional options + Apply, bytes
  in/out, never URLs). Root re-exports added.
- imagegen.Editor (ADR-0018): optional image-to-image interface —
  EditRequest carries the generation knobs plus Init image and
  denoising Strength; separate interface so existing Models keep
  compiling.
- provider/llamaswap implements all of it: POST /v1/audio/speech (JSON,
  raw-audio response, MIME from Content-Type with format fallback),
  POST /v1/audio/transcriptions (multipart, response_format=json),
  ListVoices (GET /v1/audio/voices?model=, tolerant of string-list and
  object-list shapes), POST /sdapi/v1/img2img (txt2img wire +
  init_images/denoising_strength, shared image decode), and Health(ctx)
  (GET /health) — a cheap liveness probe for often-offline hosts.
- Hermetic httptest coverage for every new wire shape and validation
  path; README sections + support-matrix footnote updated in the same
  commit (also corrects the stale /v1/images/generations claim — the
  image path has been SDAPI since the seed fix).

First consumer: mort's llamaswap media tool cluster (status / image /
TTS / STT agent tools against the netherstorm host).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AXQxVhXBw8PwFAtsVrXSmj

majordomo.go

@@ -26,6 +26,7 @@ import (
 	"encoding/json"
 	"sync"
 
+	"gitea.stevedudenhoeffer.com/steve/majordomo/audio"
 	"gitea.stevedudenhoeffer.com/steve/majordomo/imagegen"
 	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
 )
@@ -67,6 +68,26 @@ type (
 	ImageResult      = imagegen.Result
 	ImageOption      = imagegen.Option
 	ImageModelOption = imagegen.ModelOption
+	ImageEditor      = imagegen.Editor
+	ImageEditRequest = imagegen.EditRequest
+	ImageEditOption  = imagegen.EditOption
+)
+
+// Re-exported canonical speech types. See the audio package for
+// documentation. Speech synthesis and transcription are separate contracts
+// from llm, mirroring imagegen (ADR-0017); the first backend is
+// provider/llamaswap.
+type (
+	SpeechModel           = audio.SpeechModel
+	SpeechProvider        = audio.SpeechProvider
+	SpeechRequest         = audio.SpeechRequest
+	SpeechResult          = audio.SpeechResult
+	SpeechOption          = audio.SpeechOption
+	TranscriptionModel    = audio.TranscriptionModel
+	TranscriptionProvider = audio.TranscriptionProvider
+	TranscriptionRequest  = audio.TranscriptionRequest
+	TranscriptionResult   = audio.TranscriptionResult
+	TranscriptionOption   = audio.TranscriptionOption
 )
 
 // Re-exported role and finish-reason constants.