add importing from prefix

src/prefixes.js

@@ -42,6 +42,24 @@ function prefixExists(name) {
   }
 }
 
+// Where the Windows C: drive of a prefix actually lives: plain wine keeps
+// it at the top (WINEPREFIX=<prefix>), Proton-managed prefixes nest it
+// under pfx/ (WINEPREFIX=<prefix>/pfx). system.reg marks the real prefix
+// root; a fresh prefix may not have it yet, so fall back to drive_c itself.
+function prefixDriveRoot(name) {
+  const root = prefixPath(name)
+  for (const pass of [true, false]) {
+    for (const base of [root, path.join(root, 'pfx')]) {
+      try {
+        const driveC = path.join(base, 'drive_c')
+        if (!fs.statSync(driveC).isDirectory()) continue
+        if (!pass || fs.existsSync(path.join(base, 'system.reg'))) return driveC
+      } catch {}
+    }
+  }
+  return null
+}
+
 function createPrefix(name) {
   const clean = normalizeName(name)
   if (!clean) return { ok: false, error: 'invalidName' }
@@ -75,4 +93,4 @@ function setDefaultPrefix(name) {
   return { ok: true }
 }
 
-module.exports = { listPrefixes, createPrefix, deletePrefix, setDefaultPrefix, prefixPath, prefixExists, normalizeName, MAIN }
+module.exports = { listPrefixes, createPrefix, deletePrefix, setDefaultPrefix, prefixPath, prefixExists, prefixDriveRoot, normalizeName, MAIN }