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/npm.yml

@@ -0,0 +1,21 @@
+name: npm
+description: Profile for npm, extending npm-restrictive with npm environment variables
+inherits: npm-restrictive
+
+package_managers:
+  - npm
+
+environment:
+  # The npm-restrictive base allows no environment variables. Re-allow only
+  # what npm needs for auth, registry config, and TLS.
+  #
+  # Accepted trade-off: a malicious JS package executed during install can read
+  # the npm publishing token below, but NOT yarn/bun tokens, PyPI tokens, AWS
+  # keys, or other cloud/secret-manager credentials, which remain scrubbed.
+  allow:
+    - NPM_TOKEN
+    - NPM_AUTH_TOKEN
+    - NODE_AUTH_TOKEN
+    - npm_config_*
+    - NPM_CONFIG_*
+    - NODE_EXTRA_CA_CERTS