chore: add CODEOWNERS

## Summary
- Export `pnpm_config_pm_on_fail=download` from the action so the bootstrap pnpm switches versions via `manage-package-manager-versions` instead of throwing `BAD_PM_VERSION` when a project pins `devEngines.packageManager.onFail = "error"` without supplying a `version:` input.
- Adds a `test_dev_engines_on_fail_error` workflow job (Linux/macOS/Windows, exact + range) that reproduces #252.

Fixes #252.

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @zkochan

src/index.ts

@@ -8,16 +8,16 @@ import pnpmInstall from './pnpm-install'
 import pruneStore from './pnpm-store-prune'
 
 async function main() {
-  const inputs = getInputs()
-
   if (getState('is_post') === 'true') {
-    await runPost(inputs)
+    await runPost()
   } else {
-    await runMain(inputs)
+    await runMain()
   }
 }
 
-async function runMain(inputs: Inputs) {
+async function runMain() {
+  const inputs = getInputs()
+  saveState('inputs', inputs)
   saveState('is_post', 'true')
 
   const binDest = await installPnpm(inputs)
@@ -30,7 +30,8 @@ async function runMain(inputs: Inputs) {
   pnpmInstall(inputs)
 }
 
-async function runPost(inputs: Inputs) {
+async function runPost() {
+  const inputs = JSON.parse(getState('inputs')) as Inputs
   pruneStore(inputs)
   await saveCache(inputs)
 }