V271 - Characters/<accountname>, native BG2 Import/Export

Canonical storage (BG2 Documents/profile folder):
  characters/Drakhysys/ -> Drakhysys CHR and BIO files
  characters/Kronas/    -> Kronas CHR and BIO files

Create account creates characters/<accountname> with case-preserved display name.
Login allows only its own character folder. Normal BG2 Import and Export UI,
filename selection, Done, Cancel and character-creation Accept are preserved.

Because the BG2 engine expects flat characters/*.chr, temporary NTFS hardlink
aliases of the selected account's files appear in the parent while logged in.
They are NOT copies; they reference the exact original account file. Newly
exported files written by BG2 to the flat root are moved into the correct
account folder once writing finishes, then linked into the native view.
The router checks for changes every 0.1s; no automatic backup is created.
Aliases are unlinked on logout; the actual account files remain in subfolders.
Do not use with two different accounts simultaneously sharing the same BG2
Documents profile. OS-level Windows NTFS hardlink support is required.

Existing files or old version account folders are never automatically moved.
With BG2 closed, manually relocate old characters_<accountname> folders into
characters/<accountname>, keeping the _DRAKHYSYS_ACCOUNT_FLAG.json within them.
If shared CHR/BIO files already exist directly in characters/, move them
manually into their intended account before logging in. Do not delete them.

Re-run SETUP_IN_GAME_ACCOUNTS.bat with ALL BG2 windows closed after installation.
WARNING: Native in-game behavior and Windows NTFS links must be tested on Windows;
this package was statically and filesystem-tested outside BG2.
