Refactor LSP tools and add hover functionality

- Split diagnostics tool into separate lsp-diagnostics.ts file
- Add new lsp-hover.ts tool for LSP hover information
- Update tool exports and session integration
- Remove old diagnostics.ts file

🤖 Generated with opencode
Co-Authored-By: opencode <noreply@opencode.ai>

js/src/session/session.ts

@@ -42,6 +42,7 @@ export namespace Session {
   export type Message = UIMessage<{
     time: {
       created: number;
+      completed?: number;
     };
     sessionID: string;
     tool: Record<string, Tool.Metadata>;
@@ -305,6 +306,8 @@ export namespace Session {
       }
       await write(next);
     }
+    next.metadata!.time.completed = Date.now();
+    await write(next);
     return next;
   }
 }