chore(): add telemetry event for auto mode routing fallback

src/platform/endpoint/node/automodeService.ts

@@ -240,6 +240,25 @@
 				this._logService.error(errorMsg);
 				throw new Error(errorMsg);
 			}
+			if (shouldRoute) {
+				// If routing was attempted but failed, emit event that we are falling back to the reserved model
+				{
+					/* __GDPR__
+						"automode.routerDecisionFallback" : {
+							"owner": "tyleonha",
+							"comment": "Reports a fallback event when the router fails to return a valid model and we have to fall back to the reserved model.",
+							"availableModels": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "comment": "Comma-separated list of available models for this request" },
+							"preferredModels": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "comment": "Comma-separated list of preferred models for this request, ordered by preference with the reserved model first" },
+							"chosenModel": { "classification": "SystemMetaData", "purpose": "FeatureInsight", "comment": "The fallback model used when router fails" }
+						}
+					*/
+					this._telemetryService.sendMSFTTelemetryEvent('automode.routerDecisionFallback', {
+						'availableModels': availableModels.join(','),
+						'preferredModels': preferredModels.join(','),
+						'chosenModel': selectedModel.model,
+					})
+				}
+			}
 		}
 		selectedModel = this._applyVisionFallback(chatRequest, selectedModel, reserveToken.available_models, knownEndpoints);