Triple-slash references to marker-free TypeScript files depend on import order #3593

A triple-slash path reference to a marker-free .ts file fails if a side-effect import loads the same file first.

shared.ts

const marker = 1;

referrer.ts

/// <reference path="./shared.ts" />
export {};

main.ts

import './shared';
import './referrer';
console.log('main');

SharpTS reports that the path reference cannot refer to a module file and claims shared.ts contains import/export statements. Swapping the two import lines prints main in interpretation and in saved IL with verification passing. TypeScript 6.0.3 with --module NodeNext accepts both orders, and both emitted programs print main in Node v22.23.2.

Reproduce with --no-tsconfig --noLib main.ts or --no-tsconfig --noLib --compile main.ts --verify -o main.dll. Both orders behave the same on the compiler before the #3552 follow-up changes and on PR #3577. The resolver mutates the cached IsScript after an import, then uses that value to validate a later path reference. This differs from #3547, which classifies sources with explicit ESM extensions.