V291 — Fix phantom/old Export names (based on V290)

Symptom:
BG2 may display a stale stock Export filename list (KRONAS, etc.) even
while characters/ contains no .CHR files. The game can cache old filenames
when files were removed while BG2 was open, or may be reading a different
profile directory. This release filters what is DISPLAYED against the
router-produced snapshot of actual characters/<logged account> .CHR files.

- Filters both native CHARACTER_EXPORT and CHARGEN_EXPORT filename lists.
- Uses the original, unfiltered BG2 list indexes for a selected filename.
- Native Export Done/Cancel and editable filename continue to work.
- Accepts valid BG2 names containing spaces, including 'Kronos 2'.
- Imports, per-account character folder layout, BG2 login, campaigns, and
  per-account configuration are preserved.
- Does NOT delete or move anything already inside an account folder.
- Account-owned .CHR/.BIO files are NOT backed up by this installer.
- V290's existing cleanup of unassigned root .CHR/.BIO remains in place.

INSTALL:
1. Exit ALL BG2/InfinityLoader instances before installation, and do not
   manually delete .CHR files while BG2 is running.
2. Extract the archive, run SETUP_IN_GAME_ACCOUNTS.bat, choose the correct
   BG2 installation and Documents folder holding Baldur.lua.
3. Start BG2 again and verify an empty Drakhysys folder shows no old names
   in Export; create and export a NEW uniquely named character, verify the
   .CHR appears in characters/Drakhysys, and reopen Export.
4. If the old names are still listed, or a new export is not saved, check
   whether BG2 and the router use the SAME Baldur.lua profile. Send the
   router errors/status files for diagnosis; do not delete account files.

NOTE: Empty filename lists if the router snapshot is unavailable are by
design: the UI must not show other accounts' cached names. The filename
field remains editable for a new native Export. Live Windows BG2 testing
is required; these local Lua/Python tests cannot validate the actual engine.
