cl: unwind-protect — cleanup frame in cl-eval-ast, 8 new tests (159 eval)

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

lib/common-lisp/eval.sx

@@ -309,6 +309,16 @@
                     (:else (run (+ i 1))))))))))
       (run 0))))
 
+;; ── UNWIND-PROTECT ───────────────────────────────────────────────
+
+(define cl-eval-unwind-protect
+  (fn (args env)
+    (let ((protected (nth args 0))
+          (cleanup   (rest args)))
+      (let ((result (cl-eval protected env)))
+        (for-each (fn (f) (cl-eval f env)) cleanup)
+        result))))
+
 ;; ── BLOCK / RETURN-FROM ───────────────────────────────────────────
 
 (define cl-eval-block
@@ -605,6 +615,7 @@
           ((= head "TAGBODY")      (cl-eval-tagbody args env))
           ((= head "GO")
             {:cl-type "go-tag" :tag (nth args 0)})
+          ((= head "UNWIND-PROTECT") (cl-eval-unwind-protect args env))
           ((= head "BLOCK")        (cl-eval-block args env))
           ((= head "RETURN-FROM")  (cl-eval-return-from args env))
           ((= head "RETURN")