feat(omnivoice): expose full generation surface (voice-design, language, diffusion params)

Wrapper /v1/audio/speech now accepts OmniVoice's whole surface:
- voice (clone, now OPTIONAL) and/or instruct (voice DESIGN). instruct is a CONTROLLED
  vocabulary (gender/age/pitch/accent/whisper tags, comma-separated), not free prose —
  discoverable at the new /v1/audio/instruct-items endpoint (23 items).
- language (Auto + 647, new /v1/audio/languages endpoint), speed, duration.
- diffusion controls: num_step, guidance_scale, denoise, preprocess_prompt,
  postprocess_output; plus a generation_overrides JSON passthrough for expert
  GenerationConfig knobs (t_shift, layer_penalty_factor, position/class temperature,
  audio_chunk_*).
- at least one of voice/instruct required (else 400).

Catalog (services.yaml): omnivoice v1 -> v2, 13 schema-valid fields; instruct as a
controlled-vocab text field sourced from the items endpoint.

Verified live on irv-ml1: clone, voice-design (instruct-only), and tuned-param synths
all -> 24 kHz PCM_16 WAV; 647 languages; 23 instruct items.

docs/asset-engine/services.yaml

@@ -572,7 +572,7 @@ services:
       (diffusion-LM, RTF ~0.025). Apache-2.0. Behind our own FastAPI wrapper
       (stacks/omnivoice/app.py); voices are the reused chatterbox reference clips.
     category: tts
-    version: 1
+    version: 2
     status: ready
     host: irv-ml1
     lifecycle:
@@ -592,15 +592,90 @@ services:
         label: Text
         required: true
         max_length: 5000
+      # Voice source — at least one of voice (clone) / instruct (design) is required.
       - name: voice
         type: select
-        label: Speaker Voice
+        label: Speaker Voice (clone)
+        optional: true
         source_url: http://10.100.79.3:8199/v1/audio/voices
         source_jsonpath: $.voices[*]
         description: >
-          Zero-shot clone target — a reference clip staged in
-          /worktank/omnivoice/voices/ (reused chatterbox voices; 33 at deploy).
-          Live list at /v1/audio/voices.
+          Zero-shot clone target — a reference clip in /worktank/omnivoice/voices/
+          (reused chatterbox voices; 33 at deploy). Omit to design a voice via
+          instruct instead. Live list at /v1/audio/voices.
+      - name: instruct
+        type: text
+        label: Voice Design (instruct)
+        optional: true
+        source_url: http://10.100.79.3:8199/v1/audio/instruct-items
+        source_jsonpath: $.instruct_items[*]
+        description: >
+          Voice DESIGN — a comma-separated list of CONTROLLED attribute tags (not
+          free prose), e.g. "british accent, elderly, male, low pitch". Valid tags
+          (gender/age/pitch/accent/whisper) at /v1/audio/instruct-items. Use instead
+          of, or together with, a clone voice.
+      - name: language
+        type: select
+        label: Language
+        optional: true
+        default: Auto
+        source_url: http://10.100.79.3:8199/v1/audio/languages
+        source_jsonpath: $.languages[*]
+        description: "Auto-detects when left as Auto; 600+ languages supported."
+      - name: speed
+        type: slider
+        label: Speed
+        optional: true
+        min: 0.5
+        max: 1.5
+        default: 1.0
+        description: "1.0 = normal; >1 faster, <1 slower. Ignored if duration is set."
+      - name: duration
+        type: number
+        label: Duration (seconds)
+        optional: true
+        description: "Fixed output length in seconds; overrides speed when set."
+      - name: num_step
+        type: slider
+        label: Inference Steps
+        optional: true
+        min: 4
+        max: 64
+        default: 32
+        description: "Diffusion steps. Lower = faster, higher = better quality."
+      - name: guidance_scale
+        type: slider
+        label: Guidance Scale (CFG)
+        optional: true
+        min: 0.0
+        max: 4.0
+        default: 2.0
+      - name: denoise
+        type: bool
+        label: Denoise
+        optional: true
+        default: true
+      - name: preprocess_prompt
+        type: bool
+        label: Preprocess Prompt
+        optional: true
+        default: true
+        description: "Silence-trim + punctuate the reference (clone mode)."
+      - name: postprocess_output
+        type: bool
+        label: Postprocess Output
+        optional: true
+        default: true
+        description: "Remove long silences from the generated audio."
+      - name: generation_overrides
+        type: json
+        label: Advanced (GenerationConfig)
+        optional: true
+        description: >
+          Expert OmniVoiceGenerationConfig overrides as a JSON object — keys:
+          t_shift (0.1), layer_penalty_factor (5.0), position_temperature (5.0),
+          class_temperature (0.0), audio_chunk_duration (15.0),
+          audio_chunk_threshold (30.0). Unknown keys ignored.
       - name: response_format
         type: select
         options: [wav]
@@ -621,9 +696,12 @@ services:
       warm_per_unit: "full-utterance (no streaming)"
     license: "Apache-2.0"
     notes: |
-      v1 is clone-only (voice = a staged reference clip); OmniVoice's voice-DESIGN
-      and language/instruct controls are not yet exposed in the wrapper. No streaming.
-      Voices reused from chatterbox /refs (staged into /worktank/omnivoice/voices/).
+      Two voice sources, combinable: voice (clone a staged reference clip) and/or
+      instruct (free-text voice DESIGN); at least one required. Full generation
+      surface exposed — language (600+), speed, duration, num_step, guidance_scale,
+      denoise, preprocess/postprocess — with expert GenerationConfig knobs (t_shift,
+      layer/position/class temperature, audio_chunk_*) via the generation_overrides
+      JSON field. No streaming. Voices reused from chatterbox /refs.
 
   - id: qwen3-tts
     name: Qwen3-TTS 1.7B