🧪 Add error path test for extract_manifest

🎯 **What:** Adds a missing error path test for `extract_manifest` in `compat-harness` when provided with non-existent paths.
📊 **Coverage:** The scenario where the upstream workspace or repository paths do not exist and `fs::read_to_string` fails is now tested to ensure it returns a `NotFound` error.
✨ **Result:** Improved test coverage and reliability for path resolution failure modes.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: badMade

patch_pr.py

@@ -0,0 +1,3 @@
+🎯 **What:** Adds a missing error path test for `extract_manifest` in `compat-harness` when provided with non-existent paths.
+📊 **Coverage:** The scenario where the upstream workspace or repository paths do not exist and `fs::read_to_string` fails is now tested to ensure it returns a `NotFound` error.
+✨ **Result:** Improved test coverage and reliability for path resolution failure modes.

pr_body.txt

@@ -354,4 +354,12 @@ mod tests {
         assert!(names.contains(&"AgentTool"));
         assert!(names.contains(&"BashTool"));
     }
+
+    #[test]
+    fn extract_manifest_returns_error_for_non_existent_paths() {
+        let paths = UpstreamPaths::from_repo_root("/does/not/exist/anywhere/12345");
+        let result = extract_manifest(&paths);
+        assert!(result.is_err());
+        assert_eq!(result.unwrap_err().kind(), std::io::ErrorKind::NotFound);
+    }
 }