refactor(server): tidy webhook wiring and test-helper context

- Distinguish the two GitHub webhook auth-failure warn messages (missing
  signature header vs. HMAC mismatch) so logs can tell them apart.
- Route update_github_app_webhook through fabro_github::github_api_base_url()
  so GITHUB_BASE_URL overrides the webhook config endpoint too.
- Drop a narrative shutdown comment that restated the next two lines.
- Replace concat!(file!(), ":", line!()) inside local test-helper wrappers;
  those macros expand at the wrapper definition site, so every panic
  reported the same phantom location. Pass the wrapper name instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/crates/fabro-server/src/github_webhooks.rs

@@ -151,8 +151,9 @@ pub(crate) async fn update_github_app_webhook(
         "content_type": "json",
     });
 
+    let url = format!("{}/app/hook/config", fabro_github::github_api_base_url());
     let resp = client
-        .patch("https://api.github.com/app/hook/config")
+        .patch(&url)
         .header("Authorization", format!("Bearer {jwt}"))
         .header("Accept", "application/vnd.github+json")
         .header("User-Agent", "fabro")

lib/crates/fabro-server/src/ip_allowlist.rs

@@ -345,7 +345,7 @@ mod tests {
     }
 
     async fn assert_status(response: axum::response::Response, expected: StatusCode) {
-        assert_axum_status(response, expected, concat!(file!(), ":", line!())).await;
+        assert_axum_status(response, expected, "assert_status").await;
     }
 
     #[test]

lib/crates/fabro-server/src/jwt_auth.rs

@@ -299,11 +299,11 @@ mod tests {
     }
 
     async fn response_json(response: axum::response::Response) -> serde_json::Value {
-        expect_axum_json(response, StatusCode::OK, concat!(file!(), ":", line!())).await
+        expect_axum_json(response, StatusCode::OK, "response_json").await
     }
 
     async fn assert_status(response: axum::response::Response, expected: StatusCode) {
-        assert_axum_status(response, expected, concat!(file!(), ":", line!())).await;
+        assert_axum_status(response, expected, "assert_status").await;
     }
 
     fn dev_token_mode() -> AuthMode {

lib/crates/fabro-server/src/serve.rs

@@ -649,7 +649,6 @@ where
         let _ = child.wait();
     }
 
-    // Clean up webhook listener on shutdown
     if let Some(manager) = webhook_manager {
         manager.shutdown().await;
     }

lib/crates/fabro-server/src/server.rs

@@ -1250,12 +1250,12 @@ async fn github_webhook(
         .get("x-hub-signature-256")
         .and_then(|value| value.to_str().ok())
     else {
-        warn!(delivery = %delivery_id, "Webhook signature verification failed");
+        warn!(delivery = %delivery_id, "Webhook missing X-Hub-Signature-256 header");
         return StatusCode::UNAUTHORIZED;
     };
 
     if !verify_signature(&secret, &body, signature) {
-        warn!(delivery = %delivery_id, "Webhook signature verification failed");
+        warn!(delivery = %delivery_id, "Webhook HMAC signature mismatch");
         return StatusCode::UNAUTHORIZED;
     }
 
@@ -7416,25 +7416,25 @@ mod tests {
     }
 
     async fn assert_status(response: axum::response::Response, expected: StatusCode) {
-        assert_axum_status(response, expected, concat!(file!(), ":", line!())).await;
+        assert_axum_status(response, expected, "assert_status").await;
     }
 
     async fn checked_response(
         response: axum::response::Response,
         expected: StatusCode,
     ) -> axum::response::Response {
-        expect_axum_status(response, expected, concat!(file!(), ":", line!())).await
+        expect_axum_status(response, expected, "checked_response").await
     }
 
     async fn response_json(
         response: axum::response::Response,
         expected: StatusCode,
     ) -> serde_json::Value {
-        expect_axum_json(response, expected, concat!(file!(), ":", line!())).await
+        expect_axum_json(response, expected, "response_json").await
     }
 
     async fn response_bytes(response: axum::response::Response, expected: StatusCode) -> Vec<u8> {
-        expect_axum_bytes(response, expected, concat!(file!(), ":", line!())).await
+        expect_axum_bytes(response, expected, "response_bytes").await
     }
 
     fn api(path: &str) -> String {

lib/crates/fabro-server/src/web_auth.rs

@@ -740,18 +740,18 @@ mod tests {
     }
 
     async fn response_json(response: axum::response::Response) -> Value {
-        expect_axum_json(response, StatusCode::OK, concat!(file!(), ":", line!())).await
+        expect_axum_json(response, StatusCode::OK, "response_json").await
     }
 
     async fn assert_status(response: axum::response::Response, expected: StatusCode) {
-        assert_axum_status(response, expected, concat!(file!(), ":", line!())).await;
+        assert_axum_status(response, expected, "assert_status").await;
     }
 
     async fn checked_response(
         response: axum::response::Response,
         expected: StatusCode,
     ) -> axum::response::Response {
-        fabro_test::expect_axum_status(response, expected, concat!(file!(), ":", line!())).await
+        fabro_test::expect_axum_status(response, expected, "checked_response").await
     }
 
     #[tokio::test]