fix: DH-21945: Missing panel url and removed unused tool (#318)

DH-21945:
- Fixed a bug where `panelUrlFormat` was undefined if passing DHE server
URL to `listVariables` tool
- Removed unused `setEditorConnection` tool

### Testing
- Connect to qa-gplus and run
```py
from deephaven import time_table
simple_ticking = time_table("PT2S")
```
- Copy / paste the following prompt into Copilot chat
```
#listVariables
explicitly pass https://qa-gplus-java17-cluster-infra-1.int.illumon.com:8000/ as connectionUrl.
Tell me if panelUrlFormat is populated
```

Author: bmingles

src/mcp/McpServer.ts

@@ -26,7 +26,6 @@ import {
   createRemoveRemoteFileSourcesTool,
   createRunCodeFromUriTool,
   createRunCodeTool,
-  createSetEditorConnectionTool,
   createShowOutputPanelTool,
 } from './tools';
 import { OutputChannelWithHistory, withResolvers } from '../util';
@@ -74,7 +73,6 @@ export class McpServer extends DisposableBase {
     this.registerTool(createRemoveRemoteFileSourcesTool());
     this.registerTool(createRunCodeFromUriTool(this));
     this.registerTool(createRunCodeTool(this));
-    this.registerTool(createSetEditorConnectionTool(this));
     this.registerTool(createShowOutputPanelTool(this));
   }
 

src/mcp/tools/index.ts

@@ -12,5 +12,4 @@ export * from './getTableData';
 export * from './removeRemoteFileSources';
 export * from './runCode';
 export * from './runCodeFromUri';
-export * from './setEditorConnection';
 export * from './showOutputPanel';

src/mcp/tools/setEditorConnection.spec.ts

@@ -285,6 +285,48 @@ describe('serverUtils', () => {
           serverManager
         );
       });
+
+      it('should use connection.serverUrl when DHE server URL differs from connection URL', async () => {
+        const dheServerUrl = new URL('http://deephaven-server:8000');
+        const workerUrl = new URL('http://deephaven-server:8000/worker/abc');
+        const mockPanelUrlFormat = 'mock.panelUrlFormat';
+
+        const connectionWithDifferentUrl = createMockDhcService({
+          serverUrl: workerUrl,
+        });
+
+        const runningDheServerWithDifferentUrl = {
+          url: dheServerUrl,
+          type: 'DHE',
+          isRunning: true,
+        } as ServerState;
+
+        vi.mocked(serverManager.getServer).mockReturnValue(
+          runningDheServerWithDifferentUrl
+        );
+        vi.mocked(serverManager.getConnections).mockReturnValue([
+          connectionWithDifferentUrl,
+        ]);
+        vi.mocked(getDhePanelUrlFormat).mockResolvedValue(mockPanelUrlFormat);
+
+        const result = await getFirstConnectionOrCreate({
+          serverManager,
+          connectionUrl: dheServerUrl,
+        });
+
+        expect(result).toEqual({
+          success: true,
+          connection: connectionWithDifferentUrl,
+          panelUrlFormat: mockPanelUrlFormat,
+        });
+
+        // Should use connection.serverUrl (workerUrl), not the DHE server URL
+        expect(getDhePanelUrlFormat).toHaveBeenCalledWith(
+          dheServerUrl,
+          workerUrl,
+          serverManager
+        );
+      });
     });
   });