Cryptext x64 0.5 file-writer test
=================================

0.5 is the first build that writes a real encrypted file. It is intentionally
constrained: the chosen source is READ ONLY and is always retained. The only
artifact left on success is a hidden same-directory file named:

  original-name.$#!.temp

Suggested first tests
---------------------
Use disposable test files even though 0.5 never opens the source for writing.
Try these plaintext sizes because they exercise record boundaries:

  0 bytes          -> expected encrypted size       136 bytes
  1 byte           -> expected encrypted size       153 bytes
  4,194,304 bytes  -> expected encrypted size 4,194,456 bytes
  4,194,305 bytes  -> expected encrypted size 4,194,473 bytes

The formula is the frozen v1 rule:
  72-byte header + 48-byte metadata + 16-byte metadata tag
  + plaintext bytes + 16 bytes per 4 MiB data record.

Test procedure
--------------
1. Start bin\Cryptext64.exe.
2. Enter any non-empty password, physically or with the protected virtual
   keyboard.
3. Click OK.
4. Select one test file in the Windows file picker.
5. Expect "Dateitest 0.5: OK".
6. Confirm that the original file's content, size and Last-Write time did not change.
   (A filesystem may update Last-Access as a consequence of reading; Cryptext
   itself never requests write access to the source.)
7. Because the output is hidden, use Explorer with hidden files enabled or:

     dir /a:h "path\to\original-name.$#!.temp"

8. Repeating the operation on the same source should NOT overwrite the existing
   temp file; 0.5 should report that it already exists.

Important
---------
- There is no final rename to .$#! yet.
- There is no decrypt path yet.
- The "Originaldatei beibehalten" checkbox is intentionally ignored in 0.5;
  the original is always kept.
- A normal error removes a partial temp. A hard crash/power loss can leave a
  hidden partial temp, which is expected for the transactional design.
