fix: reconcile ambiguous merge outcomes (#277)

frontend/pull-sheet.js

@@ -139,7 +139,11 @@ function createPullSheet({ fetchJson, storage, createConversationPager = globalT
         headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
         body: JSON.stringify({ expected_head_sha: expectedHeadSha }),
       }).then(result => {
-        if (!result?.merged) throw new Error('Pull request merge was not confirmed.');
+        if (!result?.merged) {
+          throw new Error(result?.confirmation_pending && result?.error
+            ? result.error
+            : 'Pull request merge was not confirmed.');
+        }
         return result;
       }).finally(() => { mergeRequest = null; });
       return mergeRequest;