Fix unvalidated TerminalProfileSize during distribution import (#41495)

* Fix unvalidated TerminalProfileSize when importing a distribution

_ProcessImportResultMessage constructed the terminal profile string_view
using the message-supplied TerminalProfileSize without validating it
against the received buffer length. Use the bounds-checked two-argument
span::subspan() overload (matching the existing ShortcutIconSize handling
a few lines above) so an inconsistent size value throws instead of
producing a string_view that runs past the end of the buffer.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 35281c30-3d08-4f05-8c84-2ce4711023d5

* format source

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Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 35281c30-3d08-4f05-8c84-2ce4711023d5