Fix parsing WinGet uninstall commands with dotted arguments

[BreezeDelegate]

Summary

Fix command parsing for uninstall strings that use a bare executable name with dotted arguments, such as:

winget uninstall --product-code Exiv2.Exiv2_Microsoft.Winget.Source_8wekyb3d8bbwe

SeparateArgsFromCommand currently sees the first . in the package identifier and treats the entire command line as the executable path. This makes Process.Start try to launch the full string as a file.

The same parser failure also explains #779, which reports the equivalent command shape with mikf.gallery-dl_Microsoft.Winget.Source_8wekyb3d8bbwe.

The existing parser now gets the first chance to split valid paths and executable names. A bare-executable fallback is only used when dotted arguments otherwise leave the whole command looking like a filename. This preserves existing unquoted executable names that contain spaces.

Fixes #971.
Fixes #779.

Validation

• current master: the reported WinGet command is parsed as the entire executable path, reproducing the failure from Consistently fails to uninstall WinGet packages #971/Error: File doesn't exist (it does) #779
• actual ProcessTools.SeparateArgsFromCommand matrix: 7/7 passed under a self-contained win-x64 run, covering both reported WinGet product codes, cmd, msiexec, quoted/unquoted paths with spaces, and an unquoted executable name containing spaces
• adversarial regression check: the first implementation parsed My Uninstaller.exe /S as My + Uninstaller.exe /S; the final implementation preserves My Uninstaller.exe + /S
• KlocTools Release build: 0 warnings, 0 errors
• git diff --check: clean

A full solution test run is not available on the Linux validation host because UninstallTools uses COM references requiring the Windows/.NET Framework MSBuild path.