catalog(fish-s2): opt references into togglable; catalog_version 1->2

asset-engine shipped the per-field enable-toggle (v0.1.14/.15) — the
durable fix for the "form submits untouched fields" family. A field
marked togglable:true renders with an OFF-by-default switch: while off
the control is disabled (excluded from submission) AND the server skips
injecting its default, so it is genuinely not sent until the user opts
in.

Per operator direction, opt fish-s2's `references` (inline-base64
Custom-clone) field in — it already satisfies the togglable-requires-
optional validator (optional:true, no default). The advanced clone
field now renders dormant and can never silently override the Voice
dropdown again.

This is a SCHEMA change (new CatalogField property), so:
- services.schema.json: add `togglable` (boolean, default false),
  mirroring the asset_engine Pydantic model that generates this schema.
- catalog_version 1 -> 2 (header: bump on schema changes).
- CATALOG-CONTRACT.md: consumer pin note -> catalog_version=2.

Scoped to `references` only. The chatterbox/dia2 clone fields are the
same family but NOT toggled: dia2 deliberately defaults voice_mode=clone
+ a clone ref as its stable out-of-box voice, and toggling that field
would change dia2's default-voice behavior (the earlier 404 fix).

Validated: jsonschema accepts togglable; additionalProperties:false
guard still rejects unknown props.

docs/asset-engine/CATALOG-CONTRACT.md

@@ -144,7 +144,7 @@ reference implementation of this pattern; copy the script shape from
 
 | Consumer                                    | Vendored at                          | Pin policy        |
 |---------------------------------------------|--------------------------------------|-------------------|
-| `asset_engine` (FastAPI/HTMX UI; ~/development/asset_engine/) | `data/services.yaml` + `data/services.yaml.lock` | catalog_version=1 |
+| `asset_engine` (FastAPI/HTMX UI; ~/development/asset_engine/) | `data/services.yaml` + `data/services.yaml.lock` | catalog_version=2 |
 
 When you add a consumer, add a row here in the same PR that lands
 the consumer. This list is what we audit when planning a

docs/asset-engine/services.schema.json

@@ -85,6 +85,12 @@
           "title": "Optional",
           "type": "boolean"
         },
+        "togglable": {
+          "default": false,
+          "description": "When true, the consumer renders this field with an OFF-by-default enable switch; while off the control is disabled (excluded from submission) AND the field's default is NOT injected, so it is genuinely not sent until the user opts in. Requires optional=true. Used to keep advanced override fields (e.g. inline clone references) from silently overriding primary controls.",
+          "title": "Togglable",
+          "type": "boolean"
+        },
         "default": {
           "default": null,
           "title": "Default"

docs/asset-engine/services.yaml

@@ -16,7 +16,7 @@
 # specific service's parameter shape changes. Both let downstream
 # consumers detect drift.
 
-catalog_version: 1
+catalog_version: 2
 
 services:
   - id: kokoro
@@ -763,6 +763,7 @@ services:
         label: Custom clone (inline base64)
         section: advanced
         optional: true
+        togglable: true
         description: >
           Power-use: zero-shot clone from a reference NOT in the staged library
           — array of {audio: <base64-encoded WAV bytes>, text: "transcript"}.