Use explicit extensions for imports within src (#58421)

src/server/session.ts

@@ -136,7 +136,7 @@ import {
     unmangleScopedPackageName,
     version,
     WithMetadata,
-} from "./_namespaces/ts";
+} from "./_namespaces/ts.js";
 import {
     AuxiliaryProject,
     CloseFileWatcherEvent,
@@ -180,8 +180,8 @@ import {
     stringifyIndented,
     toNormalizedPath,
     updateProjectIfDirty,
-} from "./_namespaces/ts.server";
-import * as protocol from "./protocol";
+} from "./_namespaces/ts.server.js";
+import * as protocol from "./protocol.js";
 
 interface StackTraceError extends Error {
     stack?: string;