Guard debug launch in constrained runspaces

[Copilot]

PowerShell debug launch can silently degrade in constrained language mode when the runspace lacks the DAP commands PSES depends on. That leaves breakpoints skipped and the session misleadingly “running.”

• Preflight constrained runspaces

  • Detect constrained language mode before launching a debug session.
  • Verify the required debug commands are available in the current runspace.
  • Abort launch early with a clear error when they are missing.

• Fail fast with actionable feedback

  • Surface the requested message explaining that debugging cannot start until the administrator adds the missing debug commands to the constrained runspace.
  • Prevents the debugger from starting in a broken state.

• Coverage

  • Added a focused test for constrained-language launch failure.

# When constrained mode is missing the debug commands, launch now stops immediately:
Cannot start debugging because you are running PowerShell in a constrained language mode that does not have the required debug commands available.
Please contact your administrator to add the debug commands to your constrained runspace.