cmd: remove internal env vars from help text

HEYGEN_MAX_RETRIES and HEYGEN_CONFIG_DIR are dev/debug plumbing,
not user-facing configuration. They still work but aren't advertised.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: somanshreddy

cmd/heygen/root.go

@@ -17,16 +17,15 @@ func newRootCmd(version string, formatter output.Formatter) *cobra.Command {
 	root := &cobra.Command{
 		Use:   "heygen",
 		Short: "HeyGen CLI — create and manage videos, avatars, and more",
-		// NOTE: env var list is hardcoded. Keep config-related entries in sync with
-		// envVarByKey in env_provider.go and update operational settings here too.
+		// NOTE: env var list is hardcoded. Keep in sync with envVarByKey in env_provider.go.
+		// Internal/dev-only env vars (HEYGEN_MAX_RETRIES, HEYGEN_CONFIG_DIR) are
+		// intentionally not listed here.
 		Long: `HeyGen CLI — create and manage videos, avatars, and more.
 
 Environment Variables:
   HEYGEN_API_KEY            API key for authentication (overrides stored credentials)
   HEYGEN_OUTPUT             Output format: json, human (default: json)
-  HEYGEN_NO_ANALYTICS       Disable analytics when set (default: enabled)
-  HEYGEN_MAX_RETRIES        Max retries for transient errors (default: 2, 0 to disable)
-  HEYGEN_CONFIG_DIR         Override config directory (default: ~/.heygen)`,
+  HEYGEN_NO_ANALYTICS       Disable analytics when set (default: enabled)`,
 		Version:       version,
 		SilenceUsage:  true, // we handle usage errors ourselves
 		SilenceErrors: true, // we handle error output ourselves