feat(antigravity-auth): add types and constants foundation

🤖 Generated with assistance of OhMyOpenCode

src/auth/antigravity/constants.ts

@@ -0,0 +1,54 @@
+/**
+ * Antigravity OAuth configuration constants.
+ * Values sourced from cliproxyapi/sdk/auth/antigravity.go
+ */
+
+// OAuth 2.0 Client Credentials
+export const ANTIGRAVITY_CLIENT_ID =
+  "1071006060591-tmhssin2h21lcre235vtolojh4g403ep.apps.googleusercontent.com"
+export const ANTIGRAVITY_CLIENT_SECRET = "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"
+
+// OAuth Callback
+export const ANTIGRAVITY_CALLBACK_PORT = 51121
+export const ANTIGRAVITY_REDIRECT_URI = `http://localhost:${ANTIGRAVITY_CALLBACK_PORT}/oauth-callback`
+
+// OAuth Scopes
+export const ANTIGRAVITY_SCOPES = [
+  "https://www.googleapis.com/auth/cloud-platform",
+  "https://www.googleapis.com/auth/userinfo.email",
+  "https://www.googleapis.com/auth/userinfo.profile",
+  "https://www.googleapis.com/auth/cclog",
+  "https://www.googleapis.com/auth/experimentsandconfigs",
+] as const
+
+// API Endpoint Fallbacks (order: daily → autopush → prod)
+export const ANTIGRAVITY_ENDPOINT_FALLBACKS = [
+  "https://daily-cloudcode-pa.sandbox.googleapis.com", // dev
+  "https://autopush-cloudcode-pa.sandbox.googleapis.com", // staging
+  "https://cloudcode-pa.googleapis.com", // prod
+] as const
+
+// API Version
+export const ANTIGRAVITY_API_VERSION = "v1internal"
+
+// Request Headers
+export const ANTIGRAVITY_HEADERS = {
+  "User-Agent": "google-api-nodejs-client/9.15.1",
+  "X-Goog-Api-Client": "google-cloud-sdk vscode_cloudshelleditor/0.1",
+  "Client-Metadata": JSON.stringify({
+    ideType: "IDE_UNSPECIFIED",
+    platform: "PLATFORM_UNSPECIFIED",
+    pluginType: "GEMINI",
+  }),
+} as const
+
+// Default Project ID (fallback when loadCodeAssist API fails)
+export const ANTIGRAVITY_DEFAULT_PROJECT_ID = ""
+
+// Google OAuth endpoints
+export const GOOGLE_AUTH_URL = "https://accounts.google.com/o/oauth2/v2/auth"
+export const GOOGLE_TOKEN_URL = "https://oauth2.googleapis.com/token"
+export const GOOGLE_USERINFO_URL = "https://www.googleapis.com/oauth2/v1/userinfo"
+
+// Token refresh buffer (refresh 60 seconds before expiry)
+export const ANTIGRAVITY_TOKEN_REFRESH_BUFFER_MS = 60_000