feat: add Astrai as a named provider (#486)

Add Astrai (https://as-trai.com) as a first-class OpenAI-compatible
provider. Astrai is an AI inference router with built-in cost
optimization, PII stripping, and compliance logging.

- Register ASTRAI_API_KEY env var in resolve_api_key
- Add "astrai" entry in provider factory → as-trai.com/v1
- Add factory_astrai unit test
- Add Astrai to compatible provider test list
- Update README provider count (22+ → 23+) and list

Co-authored-by: Maya Walcher <maya.walcher@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/providers/compatible.rs

@@ -894,6 +894,7 @@ mod tests {
             make_provider("Groq", "https://api.groq.com/openai", None),
             make_provider("Mistral", "https://api.mistral.ai", None),
             make_provider("xAI", "https://api.x.ai", None),
+            make_provider("Astrai", "https://as-trai.com/v1", None),
         ];
 
         for p in providers {

src/providers/mod.rs

@@ -138,6 +138,7 @@ fn resolve_provider_credential(name: &str, credential_override: Option<&str>) ->
         "opencode" | "opencode-zen" => vec!["OPENCODE_API_KEY"],
         "vercel" | "vercel-ai" => vec!["VERCEL_API_KEY"],
         "cloudflare" | "cloudflare-ai" => vec!["CLOUDFLARE_API_KEY"],
+        "astrai" => vec!["ASTRAI_API_KEY"],
         _ => vec![],
     };
 
@@ -313,6 +314,11 @@ pub fn create_provider_with_url(
             ),
         )),
 
+        // ── AI inference routers ─────────────────────────────
+        "astrai" => Ok(Box::new(OpenAiCompatibleProvider::new(
+            "Astrai", "https://as-trai.com/v1", key, AuthStyle::Bearer,
+        ))),
+
         // ── Bring Your Own Provider (custom URL) ───────────
         // Format: "custom:https://your-api.com" or "custom:http://localhost:1234"
         name if name.starts_with("custom:") => {
@@ -651,6 +657,13 @@ mod tests {
         assert!(create_provider("build.nvidia.com", Some("nvapi-test")).is_ok());
     }
 
+    // ── AI inference routers ─────────────────────────────────
+
+    #[test]
+    fn factory_astrai() {
+        assert!(create_provider("astrai", Some("sk-astrai-test")).is_ok());
+    }
+
     // ── Custom / BYOP provider ─────────────────────────────
 
     #[test]