Fix MCP transport compatibility and batch_store e2e coverage

src/auth.rs

@@ -90,6 +90,15 @@ pub fn get_optional_agent_id(headers: &HeaderMap) -> Option<String> {
         .map(ToOwned::to_owned)
 }
 
+pub fn get_optional_agent_type(headers: &HeaderMap) -> Option<String> {
+    headers
+        .get("X-Agent-Type")
+        .and_then(|v| v.to_str().ok())
+        .map(str::trim)
+        .filter(|value| !value.is_empty())
+        .map(ToOwned::to_owned)
+}
+
 /// Extract agent ID from request headers or default
 pub fn get_agent_id(request: &Request) -> String {
     get_optional_agent_id(request.headers())
@@ -122,4 +131,15 @@ mod tests {
             Some("agent-zero")
         );
     }
+
+    #[test]
+    fn extracts_agent_type_from_header() {
+        let mut headers = HeaderMap::new();
+        headers.insert("X-Agent-Type", HeaderValue::from_static("codex"));
+
+        assert_eq!(
+            get_optional_agent_type(&headers).as_deref(),
+            Some("codex")
+        );
+    }
 }