fix: name build outputs after the exports map paths

[unrevised6419]

What does it do?

Writes each build output to the path its exports condition points at, instead of always writing index.mjs (ESM) and index.js (CommonJS).

• createViteConfig takes the output file names from bundle.output.esm / bundle.output.cjs (the import / require paths), relative to the output directory. build and watch both use it, so both behave the same.
• ./strapi-admin and ./strapi-server now need only one of import or require, not both. ESM-only and CJS-only plugins can now be built. verify already allowed this.
• build warns when an extension makes Node load a file in the wrong module format: require → .js in a "type": "module" package, or import → .js in a package that isn't "type": "module". It's a warning, not an error, so existing builds keep working.
• If import and require point to different directories, the build now fails with a clear error. Before, it silently wrote both files into the require directory. Supporting split directories would need a separate Vite build per format, because emptyOutDir must not clear a shared parent such as dist.

init still writes "type": "commonjs" with index.mjs / index.js, which stays correct. Plugins that follow that layout get exactly the same files as before.

Why is it needed?

"type": "module" plugins can't be built correctly today. CommonJS always lands in index.js, which Node loads as ESM in such a package, so Strapi fails at boot with exports is not defined in ES module scope. A require: ./dist/server/index.cjs path is never written, and ESM-only plugins are rejected by validation (exports["./strapi-server"].require is a required field). Details and repro are in #242.

How to test it?

pnpm check covers it. New tests:

• src/__tests__/e2e/build.test.ts
  • a "type": "module" plugin with import: ./dist/server/index.js and require: ./dist/server/index.cjs builds exactly index.cjs and index.js, and a child Node process loads both, through require and import;
  • the .js CommonJS warning is logged for a "type": "module" package;
  • an ESM-only plugin builds only dist/server/index.js, and it loads through import.
• src/__tests__/e2e/verify.test.ts: verify passes for the built ESM-only plugin.
• New fixtures: esm-type-plugin, esm-only-plugin.

Without the source changes, 5 of the new tests fail. Existing tests are unchanged and pass.

Related issue(s)/PR(s)

Closes #242

Related: #241 (type declarations have the same one-file-for-both-formats problem; not addressed here). It touches the same files as #239 (--bundle). Whichever merges second needs a small rebase: #239 renames BundleConfig.type to name, and the new messages here use bundle.type.

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🦋 Changeset detected

Latest commit: 24659d4

The changes in this PR will be included in the next version bump.

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@strapi/sdk-plugin	Patch

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[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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