passepartout: v0.4.3 Shell Sandboxing & Safety Classification

- bwrap sandbox: detect bwrap binary, wrap shell commands through
  Linux namespace isolation with --unshare-net --unshare-ipc
  when available, fall back to timeout bash -c otherwise
- Severity classification: extend shell-blocked patterns with
  :catastrophic/:dangerous/:moderate/:harmless severity tiers,
  dispatcher-severity-max for tier comparison
- dispatcher-check-shell-safety: returns (:matched <names> :severity <tier>)
- Version: 0.4.2 -> 0.4.3 across handshake, ASDF, README badge

passepartout.asd

@@ -1,7 +1,7 @@
 (defsystem :passepartout
   :name "Passepartout"
   :author "Amr Gharbeia"
-  :version "0.4.2"
+  :version "0.4.3"
   :license "AGPLv3"
   :description "The Probabilistic-Deterministic Lisp Machine"
   :depends-on (:usocket :bordeaux-threads :dexador :uiop :cl-dotenv :cl-ppcre :hunchentoot :ironclad :str :cl-json :uuid)