Add uvx support

Add uvx as a supported package manager so that `uvx` commands are
routed through safe-chain's MITM proxy for malware detection, just
like `uv`. Previously, `uvx` bypassed all safe-chain protections.

The uvx package manager reuses the existing uv command runner since
uvx is functionally equivalent to `uv tool run`.

Fixes #268

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -52,6 +52,10 @@ function uv {
     Invoke-WrappedCommand "uv" $args $MyInvocation.Line $MyInvocation.OffsetInLine
 }
 
+function uvx {
+    Invoke-WrappedCommand "uvx" $args $MyInvocation.Line $MyInvocation.OffsetInLine
+}
+
 function poetry {
     Invoke-WrappedCommand "poetry" $args $MyInvocation.Line $MyInvocation.OffsetInLine
 }