fix: harden import preflight admission

Keep configured size-limit counts identical to real queue admission, invalidate cancelled import generations, preserve explicit empty destination choices, normalize Windows namespace aliases, inspect files through one read handle, and retain exact rejection balances.

main.js

@@ -55,7 +55,7 @@ const { buildFailedUploadSummary, buildTerminalJobSnapshots } = require('./lib/u
 const { selectPublicUploadUrl } = require('./lib/upload-confirmation');
 const { createBatchMutationGate } = require('./lib/batch-mutation-gate');
 const { createUploadStartReservation } = require('./lib/upload-start-reservation');
-const { inspectImportEntries } = require('./lib/import-preflight');
+const { inspectImportEntries, inspectReadableImportPath } = require('./lib/import-preflight');
 
 const _eventLoopDelay = monitorEventLoopDelay({ resolution: 10 });
 _eventLoopDelay.enable();
@@ -2255,22 +2255,7 @@ ipcMain.handle('inspect-import-files', async (_event, payload) => {
     existingPaths: input.existingPaths,
     filenameFilter: currentConfig.globalSettings?.filenameFilter,
     concurrency: 8,
-    inspectPath: async filePath => {
-      let fileStat;
-      try {
-        fileStat = await fs.promises.stat(filePath);
-      } catch (error) {
-        if (error && error.code === 'ENOENT') return { exists: false };
-        return { exists: true, readable: false };
-      }
-      if (!fileStat.isFile()) return { exists: true, readable: false, size: fileStat.size };
-      try {
-        await fs.promises.access(filePath, fs.constants.R_OK);
-      } catch {
-        return { exists: true, readable: false, size: fileStat.size };
-      }
-      return { exists: true, readable: true, size: fileStat.size };
-    }
+    inspectPath: filePath => inspectReadableImportPath(filePath, fs.promises.open)
   });
 });