fix(updater): use robocopy mirror on Windows to remove obsolete DLLs and assets during in-place updates #1377

Problem

In lib/core/updater/installers/update_install_utils.dart (buildWindowsReplaceBatch), the generated Windows batch script executes:

xcopy /E /Y /I "%SRC%\\*" "%DST%\\"

Unlike Linux (buildLinuxBundleReplaceScript), which uses rsync -a --delete --exclude='QueryaData' --exclude='.portable' to clean up deleted/renamed files, xcopy is purely additive:

1. Renamed, replaced, or deleted DLLs (e.g. Flutter engine upgrades, native plugin binaries, ICU data files) from the previous installation remain indefinitely in the application directory.
2. Windows DLL search order can lead to stale binary loading, symbol mismatch crashes, or corrupted asset bundles after an in-place update.
3. Portable mode directories (QueryaData, .portable) are not explicitly protected from being overwritten if the archive contains default assets matching those paths.

Solution

Replace xcopy in buildWindowsReplaceBatch with robocopy /MIR:

robocopy "%SRC%" "%DST%" /MIR /XD "QueryaData" /XF ".portable" /R:2 /W:1
if %ERRORLEVEL% GEQ 8 (
  echo Update failed with error %ERRORLEVEL%
  exit /b %ERRORLEVEL%
)
start "" "%EXE%"
del "%~f0"

• /MIR synchronizes and removes files in the destination that no longer exist in the new release bundle.
• /XD "QueryaData" and /XF ".portable" preserve portable configuration and user data across updates.
• robocopy returns exit codes 0–7 on successful synchronization (e.g. 1 = files copied, 2 = extra files removed). Only exit codes >= 8 indicate fatal errors.