fix(cli): migrate Gemini models to explicit antigravity- prefix for quota routing

All Gemini model references now use the `antigravity-` prefix to ensure explicit
routing to Antigravity quota pools instead of relying on legacy `-preview` suffix
disambiguation. This approach prevents potential breakage if Google removes the
`-preview` suffix in future versions.

Updates include:
- config-manager: Updated Gemini model assignments with antigravity- prefix
- config-manager.test.ts: Updated test assertions to match new naming convention
- install.ts: Updated config summary display to show antigravity-prefixed model name

Migration follows opencode-antigravity-auth plugin v1.2.7+ guidance for explicit
quota routing configuration.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/cli/config-manager.test.ts

@@ -11,9 +11,9 @@ describe("config-manager ANTIGRAVITY_PROVIDER_CONFIG", () => {
     expect(models).toBeTruthy()
 
     const required = [
-      "gemini-3-pro-high",
-      "gemini-3-pro-low",
-      "gemini-3-flash",
+      "antigravity-gemini-3-pro-high",
+      "antigravity-gemini-3-pro-low",
+      "antigravity-gemini-3-flash",
     ]
 
     for (const key of required) {

src/cli/config-manager.ts

@@ -279,8 +279,10 @@ export function generateOmoConfig(installConfig: InstallConfig): Record<string,
 
   agents["librarian"] = { model: "opencode/glm-4.7-free" }
 
+  // Gemini models use `antigravity-` prefix for explicit Antigravity quota routing
+  // @see ANTIGRAVITY_PROVIDER_CONFIG comments for rationale
   if (installConfig.hasGemini) {
-    agents["explore"] = { model: "google/gemini-3-flash" }
+    agents["explore"] = { model: "google/antigravity-gemini-3-flash" }
   } else if (installConfig.hasClaude && installConfig.isMax20) {
     agents["explore"] = { model: "anthropic/claude-haiku-4-5" }
   } else {
@@ -294,9 +296,9 @@ export function generateOmoConfig(installConfig: InstallConfig): Record<string,
   }
 
   if (installConfig.hasGemini) {
-    agents["frontend-ui-ux-engineer"] = { model: "google/gemini-3-pro-high" }
-    agents["document-writer"] = { model: "google/gemini-3-flash" }
-    agents["multimodal-looker"] = { model: "google/gemini-3-flash" }
+    agents["frontend-ui-ux-engineer"] = { model: "google/antigravity-gemini-3-pro-high" }
+    agents["document-writer"] = { model: "google/antigravity-gemini-3-flash" }
+    agents["multimodal-looker"] = { model: "google/antigravity-gemini-3-flash" }
   } else {
     const fallbackModel = installConfig.hasClaude ? "anthropic/claude-opus-4-5" : "opencode/glm-4.7-free"
     agents["frontend-ui-ux-engineer"] = { model: fallbackModel }
@@ -497,25 +499,39 @@ export async function runBunInstallWithDetails(): Promise<BunInstallResult> {
   }
 }
 
+/**
+ * Antigravity Provider Configuration
+ *
+ * IMPORTANT: Model names MUST use `antigravity-` prefix for stability.
+ *
+ * The opencode-antigravity-auth plugin supports two naming conventions:
+ * - `antigravity-gemini-3-pro-high` (RECOMMENDED, explicit Antigravity quota routing)
+ * - `gemini-3-pro-high` (LEGACY, backward compatible but may break in future)
+ *
+ * Legacy names rely on Gemini CLI using `-preview` suffix for disambiguation.
+ * If Google removes `-preview`, legacy names may route to wrong quota.
+ *
+ * @see https://github.com/NoeFabris/opencode-antigravity-auth#migration-guide-v127
+ */
 export const ANTIGRAVITY_PROVIDER_CONFIG = {
   google: {
     name: "Google",
     models: {
-      "gemini-3-pro-high": {
+      "antigravity-gemini-3-pro-high": {
         name: "Gemini 3 Pro High (Antigravity)",
         thinking: true,
         attachment: true,
         limit: { context: 1048576, output: 65535 },
         modalities: { input: ["text", "image", "pdf"], output: ["text"] },
       },
-      "gemini-3-pro-low": {
+      "antigravity-gemini-3-pro-low": {
         name: "Gemini 3 Pro Low (Antigravity)",
         thinking: true,
         attachment: true,
         limit: { context: 1048576, output: 65535 },
         modalities: { input: ["text", "image", "pdf"], output: ["text"] },
       },
-      "gemini-3-flash": {
+      "antigravity-gemini-3-flash": {
         name: "Gemini 3 Flash (Antigravity)",
         attachment: true,
         limit: { context: 1048576, output: 65536 },

src/cli/install.ts

@@ -49,7 +49,7 @@ function formatConfigSummary(config: InstallConfig): string {
   const sisyphusModel = config.hasClaude ? "claude-opus-4-5" : "glm-4.7-free"
   const oracleModel = config.hasChatGPT ? "gpt-5.2" : (config.hasClaude ? "claude-opus-4-5" : "glm-4.7-free")
   const librarianModel = "glm-4.7-free"
-  const frontendModel = config.hasGemini ? "gemini-3-pro-high" : (config.hasClaude ? "claude-opus-4-5" : "glm-4.7-free")
+  const frontendModel = config.hasGemini ? "antigravity-gemini-3-pro-high" : (config.hasClaude ? "claude-opus-4-5" : "glm-4.7-free")
 
   lines.push(`  ${SYMBOLS.bullet} Sisyphus     ${SYMBOLS.arrow} ${color.cyan(sisyphusModel)}`)
   lines.push(`  ${SYMBOLS.bullet} Oracle       ${SYMBOLS.arrow} ${color.cyan(oracleModel)}`)