telemetry: populate mode and use_proxy in driver_connection_params

The four Node-specific fields dropped in the previous commit have no
proto equivalent (CloudFetch enablement, LZ4, retry config, concurrent
downloads aren't tracked at the receiver). But two unrelated proto
fields can be filled from existing Node config:

  - `mode = "THRIFT"` — Node.js always uses Thrift transport (no SEA
    client). JDBC's `DatabricksClientType` enum is `SEA | THRIFT`.
  - `use_proxy` — derived from `ConnectionOptions.proxy`. Stored on
    DBSQLClient at `connect()` time alongside the existing host /
    httpPath / authType fields, then surfaced through a new
    `DriverConfiguration.useProxy` field.

Co-authored-by: Isaac

Author: samikshya-db

lib/DBSQLClient.ts

@@ -122,6 +122,8 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
 
   private authType?: string;
 
+  private useProxy?: boolean;
+
   private telemetryClient?: TelemetryClient;
 
   private telemetryEmitter?: TelemetryEventEmitter;
@@ -425,6 +427,7 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
       // Connection parameters
       httpPath: this.httpPath,
       enableMetricViewMetadata: this.config.enableMetricViewMetadata,
+      useProxy: this.useProxy,
     };
   }
 
@@ -604,6 +607,7 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
     this.host = options.host;
     this.httpPath = options.path;
     this.authType = this.mapAuthType(options);
+    this.useProxy = Boolean(options.proxy);
 
     // Store enableMetricViewMetadata configuration
     if (options.enableMetricViewMetadata !== undefined) {

lib/telemetry/DatabricksTelemetryExporter.ts

@@ -64,6 +64,8 @@ interface DatabricksTelemetryLog {
       driver_connection_params?: {
         host_info?: { host_url?: string };
         http_path?: string;
+        mode?: string;
+        use_proxy?: boolean;
         enable_arrow?: boolean;
         enable_direct_results?: boolean;
         socket_timeout?: number;
@@ -411,6 +413,8 @@ export default class DatabricksTelemetryExporter {
         log.entry.sql_driver_log.driver_connection_params = {
           host_info: { host_url: this.host },
           http_path: metric.driverConfig.httpPath,
+          mode: 'THRIFT',
+          use_proxy: metric.driverConfig.useProxy,
           enable_arrow: metric.driverConfig.arrowEnabled,
           enable_direct_results: metric.driverConfig.directResultsEnabled,
           socket_timeout: metric.driverConfig.socketTimeout,

lib/telemetry/types.ts

@@ -304,6 +304,9 @@ export interface DriverConfiguration {
 
   /** Whether metric view metadata is enabled */
   enableMetricViewMetadata?: boolean;
+
+  /** Whether an HTTP/SOCKS proxy is configured on the connection */
+  useProxy?: boolean;
 }
 
 /**