Cryptext64 0.11c smoke test
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1. Run build.bat with FASM 1.73.35.
2. Run install_shell_user.cmd while the old shell extension is installed.
   Expected: Explorer is stopped briefly, the new DLL copies without a sharing
   violation, and Explorer starts again automatically.
3. Confirm the Explorer context menu still encrypts/decrypts files.
4. Confirm .$#! still uses the Cryptext64 key/lock icon.
5. On a slow SSD / large file, watch the ~70% boundary:
   - "+ Disk-Sync" starts gray,
   - softly pulses while FlushFileBuffers is active,
   - stays black when the flush finishes,
   - then On-Disk-Verifikationsdurchlauf becomes active.
6. Confirm no "Keine Rückmeldung" state occurs during the flush.
