Add pdm package manager support

PDM is a modern Python package manager using pyproject.toml (PEP 621).
Uses the same MITM-only proxy approach as poetry/uv/pipx — all malware
detection and minimum package age enforcement happens at the proxy layer
by intercepting PyPI requests.

packages/safe-chain/src/shell-integration/startup-scripts/init-pwsh.ps1

@@ -70,6 +70,10 @@ function pipx {
     Invoke-WrappedCommand "pipx" $args $MyInvocation.Line $MyInvocation.OffsetInLine
 }
 
+function pdm {
+    Invoke-WrappedCommand "pdm" $args $MyInvocation.Line $MyInvocation.OffsetInLine
+}
+
 function Write-SafeChainWarning {
     param([string]$Command)