fix(provider): address Astrai follow-up review from #486

- Add "astrai" to factory_all_providers_create_successfully test
- Add "astrai" => "ASTRAI_API_KEY" in provider_env_var() for onboarding
- Add Astrai to onboarding provider selection list (Gateway tier)
- Add provider_env_var("astrai") assertion in known_providers test

Addresses review comments from @chumyin on #486.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/onboard/wizard.rs

@@ -1402,6 +1402,10 @@ fn setup_provider(workspace_dir: &Path) -> Result<(String, String, String, Optio
         2 => vec![
             ("vercel", "Vercel AI Gateway"),
             ("cloudflare", "Cloudflare AI Gateway"),
+            (
+                "astrai",
+                "Astrai — compliant AI routing (PII stripping, cost optimization)",
+            ),
             ("bedrock", "Amazon Bedrock — AWS managed models"),
         ],
         3 => vec![
@@ -2002,6 +2006,7 @@ fn provider_env_var(name: &str) -> &'static str {
         "bedrock" | "aws-bedrock" => "AWS_ACCESS_KEY_ID",
         "gemini" => "GEMINI_API_KEY",
         "nvidia" | "nvidia-nim" | "build.nvidia.com" => "NVIDIA_API_KEY",
+        "astrai" => "ASTRAI_API_KEY",
         _ => "API_KEY",
     }
 }
@@ -4793,6 +4798,7 @@ mod tests {
         assert_eq!(provider_env_var("nvidia"), "NVIDIA_API_KEY");
         assert_eq!(provider_env_var("nvidia-nim"), "NVIDIA_API_KEY"); // alias
         assert_eq!(provider_env_var("build.nvidia.com"), "NVIDIA_API_KEY"); // alias
+        assert_eq!(provider_env_var("astrai"), "ASTRAI_API_KEY");
     }
 
     #[test]

src/providers/mod.rs

@@ -1347,6 +1347,7 @@ mod tests {
             "cohere",
             "copilot",
             "nvidia",
+            "astrai",
         ];
         for name in providers {
             assert!(