feat: Add support for environment protection (scrubbing) (#327)

* feat: Add support for environment variable protection for sandbox

* chore: Update dangerous env var list

* fix: Split profiles for improved environment protection

* fix: pipx sandbox profile separation

* chore: Show sandbox scrub info on error exit

* fix: Code review fixes

* test: Add e2e for sandbox environment scrubbing

sandbox/profiles/pypi-restrictive.yml

@@ -3,6 +3,7 @@ description: Restrictive sandbox policy for PyPI ecosystem (pip, poetry, uv)
 package_managers:
   - pip
   - pip3
+  - pipx
   - poetry
   - uv
 
@@ -71,6 +72,15 @@ network:
   deny_outbound:
     - "*:*"
 
+environment:
+  # This profile is the shared base for the PyPI ecosystem and deliberately
+  # allows no environment variables: everything in the built-in
+  # DANGEROUS_ENV_VARS list is scrubbed. Each package manager's leaf profile
+  # (pip, uv, poetry) re-allows only the variables that package manager needs.
+  # TWINE_* is allowed nowhere: twine is not a package manager PMG wraps, so
+  # its publishing credentials stay scrubbed during installs.
+  allow: []
+
 process:
   allow_exec:
     - /usr/bin/python*