debug: add issue.assignee/assignees logging for M5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/entrypoints/run.ts

@@ -201,6 +201,12 @@ async function run() {
       console.log(
         `[M5 DEBUG] payload.assignee: ${JSON.stringify(payload.assignee)}`,
       );
+      console.log(
+        `[M5 DEBUG] payload.issue.assignee: ${JSON.stringify(payload.issue?.assignee)}`,
+      );
+      console.log(
+        `[M5 DEBUG] payload.issue.assignees: ${JSON.stringify(payload.issue?.assignees?.map((a: any) => a.login))}`,
+      );
       console.log(`[M5 DEBUG] payload.action: ${payload.action}`);
     }
     // === M5 DEBUG END ===