Update completePrompt method to include JSON representation of tool call in result string

* Serialize the tool call to JSON and append it to the result string in the `completePrompt` method

Author: Harrison-Idornigie

src/api/providers/vscode-lm.ts

@@ -596,7 +596,7 @@ export class VsCodeLmHandler extends BaseProvider implements SingleCompletionHan
 
 						// Execute the tool call
 						const toolResult = await this.executeToolCall(toolCall)
-						result += toolResult
+						result += JSON.stringify(toolCall)
 					} catch (error) {
 						console.error("Roo Code <Language Model API>: Failed to process tool call:", error)
 						// Continue processing other chunks even if one fails