ecs-persistence: [persist] on an app's components fails to compile (trait key from a package's types is 'unique symbol') #239

Summary

An app can't mark its components with [persist] as the @adobe/ecs-persistence README shows. With Compiler.plugin() the build fails:

a trait's key persist is a top-level `Symbol()` constant, of this module or one it imports
  [baseColorFactor]: { type: Vec4.F32; default: [1, 1, 1, 1]; [persist]: 'baseColorFactor' };

Repro

import { persist } from '@adobe/ecs-persistence';
export const name = Symbol();
declare module '@adobe/ecs' {
    interface Components {
        [name]: { type: string; [persist]: 'name' };
    }
}

Built with @adobe/ecs 0.2.3, @adobe/ecs-persistence 0.0.1, Vite 8 and Compiler.plugin(), in the dev server, a build and vitest alike.

Cause

The compiler reads a trait key's declaration to check that it is a Symbol() constant (requireTraitKey, augmentations.ts). For an import from a package it reads the types file beside the JavaScript (typesFileOf), and in dist/types/persist.d.ts the key is export declare const persist: unique symbol;, which is not a Symbol() call. The special case that finds a package's source applies to copies of @adobe/ecs itself, not to other packages.

Workaround

Alias @adobe/ecs-persistence to the src/index.ts the package already ships (resolve.alias), and keep it out of the dev server's pre-bundling (optimizeDeps.exclude); under vitest it also needs to be transformed by the plugin. That works but every app has to know to do it.

Requested (any of)

1. The compiler accepts a trait key whose declaration is declare const x: unique symbol in an imported package's types, since the key's identity is registered at runtime by the package's own JavaScript (declare$(persist, "trait")).
2. The compiler finds the source a package ships, as it does for @adobe/ecs, for any package that declares traits.
3. @adobe/ecs-persistence documents what an app must configure, and ships it as a Vite helper.