Move the phase entry points into aliased module folders

tests/entrypoints.test.ts

@@ -4,7 +4,7 @@ import { expect, test } from "vite-plus/test";
 
 import { runCommand } from "#testing";
 
-// Each phase runs as `node src/<phase>.ts` with no build step. Node loads the
+// Each phase runs as `node src/<phase>/index.ts` with no build step. Node loads the
 // whole import graph, stripping types, before the phase reads its first
 // variable, so failing on that variable proves every module loads.
 const PHASES: [phase: string, firstVariable: string][] = [
@@ -14,7 +14,7 @@ const PHASES: [phase: string, firstVariable: string][] = [
 ];
 
 test.each(PHASES)("Node loads the %s phase", async (phase, firstVariable) => {
-  const path = fileURLToPath(new URL(`../src/${phase}.ts`, import.meta.url));
+  const path = fileURLToPath(new URL(`../src/${phase}/index.ts`, import.meta.url));
   const result = await runCommand(process.execPath, [path], { PATH: process.env["PATH"] ?? "" });
   expect(result.success).toBe(false);
   expect(result.stderr).toContain(`${firstVariable} is not set`);