feat(presets): add OpenCode Go referral link and promo copy without partner badge

Decouple the in-app promotion banner from isPartner so a preset can show a
promo phrase plus referral link without earning the paid-partner star.

- ApiKeySection: gate the banner on partnerPromotionKey alone; the star is
  still driven solely by isPartner. This also un-suppresses the existing
  MiniMax cn/en promos, which already carried copy without isPartner.
- OpenCode Go (claude/codex/opencode): point apiKeyUrl at the referral
  link and add partnerPromotionKey "opencode_go" (no isPartner set).
- i18n: add the opencode_go promo string across zh/en/ja/zh-TW.

src/config/claudeProviderPresets.ts

@@ -282,7 +282,8 @@ export const providerPresets: ProviderPreset[] = [
   {
     name: "OpenCode Go",
     websiteUrl: "https://opencode.ai/go",
-    apiKeyUrl: "https://opencode.ai/auth",
+    apiKeyUrl: "https://opencode.ai/go?ref=2YTRG2NGTX",
+    partnerPromotionKey: "opencode_go",
     settingsConfig: {
       env: {
         ANTHROPIC_BASE_URL: "https://opencode.ai/zen/go",

src/config/codexProviderPresets.ts

@@ -802,7 +802,8 @@ requires_openai_auth = true`,
   {
     name: "OpenCode Go",
     websiteUrl: "https://opencode.ai/go",
-    apiKeyUrl: "https://opencode.ai/auth",
+    apiKeyUrl: "https://opencode.ai/go?ref=2YTRG2NGTX",
+    partnerPromotionKey: "opencode_go",
     auth: generateThirdPartyAuth(""),
     config: generateThirdPartyConfig(
       "opencode_go",

src/config/opencodeProviderPresets.ts

@@ -1049,7 +1049,8 @@ export const opencodeProviderPresets: OpenCodeProviderPreset[] = [
   {
     name: "OpenCode Go",
     websiteUrl: "https://opencode.ai/go",
-    apiKeyUrl: "https://opencode.ai/auth",
+    apiKeyUrl: "https://opencode.ai/go?ref=2YTRG2NGTX",
+    partnerPromotionKey: "opencode_go",
     settingsConfig: {
       npm: "@ai-sdk/openai-compatible",
       name: "OpenCode Go",