feat(opencode-go): complete Go catalog (40 models) with auto-fetch + family endpoint regex

- Add 12 missing models from live /zen/go/v1/models (glm-5, kimi-k2.5,
  mimo v2/v2.6 line, qwen3.5-plus, grok-4.5/4.7, omen-alpha, ...)
- modelsFetcher + passthroughModels + "opencode-go" suggested-models filter
- Family regex fallback (opencodeFamilyFormats) keeps unknown/passthrough ids
  on the right endpoint lane (/responses, /messages, /chat/completions);
  curated registry entries always win
- isResponsesModel now routes passthrough grok/gpt ids to /responses

Co-Authored-By: Claude Code <noreply@anthropic.com>

open-sse/providers/models/helpers.js

@@ -1,3 +1,5 @@
+import { FORMATS } from "../../translator/formats.js";
+
 // Codex auto-generates a "-review" variant for each llm model (review quota family)
 export const CODEX_REVIEW_SUFFIX = "-review";
 
@@ -25,3 +27,20 @@ export function isMuseSparkModel(modelId) {
   const base = clean.includes("/") ? clean.split("/").pop() : clean;
   return /^muse[-_]?spark(?:$|[-_:.\s])/i.test(base);
 }
+
+// Endpoint families for OpenCode models outside the curated registry (modelsFetcher /
+// passthrough ids) — regex keeps auto-fetched models on the right endpoint:
+// /responses (gpt/grok/muse-spark), /messages (minimax/qwen), /chat/completions (rest).
+// Curated registry entries always win; this is the unknown-id fallback only.
+const OPENCODE_FAMILIES = [
+  { match: /^(grok|gpt|muse[-_]?spark)/i, supportedFormats: [FORMATS.OPENAI_RESPONSES], targetFormat: FORMATS.OPENAI_RESPONSES },
+  { match: /^deepseek-v4-(pro|flash)/, supportedFormats: [FORMATS.OPENAI, FORMATS.CLAUDE, FORMATS.OPENAI_RESPONSES] },
+  { match: /^(minimax|qwen)/, supportedFormats: [FORMATS.OPENAI, FORMATS.CLAUDE] },
+  { match: /^claude-/i, supportedFormats: [FORMATS.CLAUDE] },
+];
+
+export function opencodeFamilyFormats(modelId) {
+  if (!modelId || typeof modelId !== "string") return null;
+  const base = modelId.replace(/\([^()]+\)\s*$/, "").trim();
+  return OPENCODE_FAMILIES.find((f) => f.match.test(base)) || null;
+}