feat(opencode-go): muse-spark-1.2 and Responses tool fixes (#3820)

- Add muse-spark-1.2-contributor as responses-only model on OpenCode Go
- Normalize object tool schemas without properties in OpenCode Go executor
- Make fallback Responses call_ids unique across same-millisecond calls
- Make Responses output coercion fail-soft for circular and non-stringifiable values

open-sse/providers/registry/opencode-go.js

@@ -52,6 +52,7 @@ export default {
     { id: "qwen3.6-plus", name: "Qwen 3.6 Plus", supportedFormats: ["openai", "claude"] },
     // Muse Spark is served by /zen/go/v1/responses only — responses-only entry forces
     // chatCore past the sourceFormat-matched transports into translation (see chatCore guard).
+    { id: "muse-spark-1.2-contributor", name: "Muse Spark 1.2 Contributor", targetFormat: "openai-responses", supportedFormats: ["openai-responses"] },
     { id: "muse-spark-1.3-contributor", name: "Muse Spark 1.3 Contributor", targetFormat: "openai-responses", supportedFormats: ["openai-responses"] },
   ],
   features: {