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.

tests/import-preflight.test.js

@@ -2,7 +2,9 @@ const { describe, it } = require('node:test');
 const assert = require('node:assert/strict');
 
 const {
+  getEligibleImportHosters,
   inspectImportEntries,
+  inspectReadableImportPath,
   summarizeImportPlan
 } = require('../lib/import-preflight');
 
@@ -81,6 +83,72 @@ describe('import preflight', () => {
     });
   });
 
+  it('uses the same configured size eligibility for summaries and queue admission', () => {
+    const file = { path: 'C:\\incoming\\large.custom', name: 'large.custom', size: 5 * 1024 * 1024 };
+    const selectedHosters = ['limited.example', 'unlimited.example', 'limited.example'];
+    const hosterSettings = {
+      'limited.example': { maxSizeMb: 3 },
+      'unlimited.example': { maxSizeMb: 0 }
+    };
+
+    assert.deepEqual(getEligibleImportHosters(file, selectedHosters, hosterSettings), ['unlimited.example']);
+    assert.deepEqual(summarizeImportPlan({
+      inspection: { candidateCount: 1, accepted: [file] },
+      selectedHosters,
+      hosterSettings
+    }), {
+      candidateCount: 1,
+      duplicateCount: 0,
+      filteredCount: 0,
+      unavailableCount: 0,
+      acceptedCount: 1,
+      targetCount: 2,
+      jobCount: 1,
+      sizeLimitedJobCount: 1
+    });
+  });
+
+  it('deduplicates Windows drive and UNC namespace aliases canonically', async () => {
+    const inspectedPaths = [];
+    const inspection = await inspectImportEntries([
+      '\\\\?\\C:\\incoming\\same.bin',
+      'C:\\incoming\\same.bin',
+      '\\\\?\\UNC\\server\\share\\same.bin',
+      '\\\\server\\share\\same.bin'
+    ], {
+      caseInsensitive: true,
+      inspectPath: async filePath => {
+        inspectedPaths.push(filePath);
+        return { exists: true, readable: true, size: 1 };
+      }
+    });
+
+    assert.equal(inspection.acceptedCount, 2);
+    assert.equal(inspection.duplicateCount, 2);
+    assert.deepEqual(inspectedPaths, ['C:\\incoming\\same.bin', '\\\\server\\share\\same.bin']);
+  });
+
+  it('inspects type and size through one opened read handle and closes it', async () => {
+    const calls = [];
+    const fileHandle = {
+      stat: async () => {
+        calls.push('stat');
+        return { isFile: () => true, size: 42 };
+      },
+      close: async () => {
+        calls.push('close');
+      }
+    };
+
+    const result = await inspectReadableImportPath('C:\\incoming\\readable.bin', async (filePath, flags) => {
+      calls.push(['open', filePath, flags]);
+      return fileHandle;
+    });
+
+    assert.deepEqual(result, { exists: true, readable: true, size: 42 });
+    assert.deepEqual(calls, [['open', 'C:\\incoming\\readable.bin', 'r'], 'stat', 'close']);
+  });
+
   it('limits concurrent file inspections', async () => {
     let active = 0;
     let maximumActive = 0;