V294 -- Prevent new cross-account exports and refresh the native Import filter

This update keeps the existing BG2 character storage and UI:
  characters/Drakhysys/*.CHR
  characters/Kronas/*.CHR

Fixes:
- When the Import list's allowed filenames change, rebuild the list even if
  BG2's cached list of native filenames is unchanged. This prevents characters
  such as KROKRO from being hidden by the prior account's Import list.
- A NEW native Export cannot be automatically moved into the current account
  if that filename already exists in another registered account folder.
  This prevents one more source of cross-account contamination.
- An existing CHR already present in both accounts is NOT deleted, relocated,
  or silently assigned to a different owner. Use AUDIT_ACCOUNT_CHARACTER_FOLDERS.bat
  to compare the contents of suspicious duplicate files before manually fixing
  them. A filename match is not proof that files are the same character.

Important:
- Because BG2 uses one shared flat native Import/Export directory, running
  two concurrent game instances against the SAME Documents profile is unsafe.
  Multiple simultaneous BG2 instances need separate profile directories.
- If an attempted new Export uses a filename already owned by another account,
  it is not adopted into the account. Use a unique export filename after confirming
  you are exporting your own character. The original other account file is untouched.
- Older duplicate files remain in place for safe manual review. No automatic
  account character backups or deletions are added here.

Install: close every BG2/InfinityLoader window, extract V294, run
SETUP_IN_GAME_ACCOUNTS.bat, and install the update. Test Kronas -> KROKRO Import,
Drakhysys -> native Export with a unique name, and verify the files in each
characters/<accountname> folder after reopening the native panels.

If you still cannot Import KROKRO, verify that it is a valid CHR file inside
characters/Kronas, not just a BIO file. Log in to Kronas, then reopen the
Import Character File panel so BG2 refreshes its native list. If needed, run
AUDIT_ACCOUNT_CHARACTER_FOLDERS.bat and share its read-only report.
