feat(issue): add body field to IssueItem type and implement issue creation and completion routes

- Added 'body' field to IssueItem type in index.ts
- Created new routes for issue creation and completion in issue.ts
- Implemented validation for required parameters in issue creation and completion
- Added a new list route for issues in list.ts

agent/routes/issues/index.ts

@@ -0,0 +1,2 @@
+import './list.ts'
+import './issue.ts'