[Copilot]

Venv CI jobs assumed the hosted runner exposed $Env:CONDA, causing setup to fail before tests when the variable was unset.

• Conda setup

  • Install Conda with a commit-pinned setup-miniconda action.
  • Preserve the matrix-selected Python by disabling environment activation.

• Path discovery

  • Resolve the first Conda executable on PATH.
  • Derive the base installation with conda info --base.
  • Record valid condaExecPath and condaPath values in envPaths.json.

• Diagnostics

  • Report explicit errors when Conda or its base Python cannot be found.

$condaCommand = Get-Command conda -CommandType Application |
    Select-Object -First 1
$condaBasePath = & $condaCommand.Source info --base

• Fixes CI venv jobs should not rely on the hosted runner's CONDA environment variable #26289