fix: 12 pre-existing test bugs — 180/185 pass

- repl: test-repl-list-vars used wrong keyword (REPL-SENSOR→PASSEPARTOUT),
  test-repl-inspect-found expected nonexistent 'function' substring
- literate: test-extract-lisp-blocks had ~% as literal chars (→format nil),
  test-block-balance-check-valid had broken path merging
- diagnostics: test-diagnostics-env-fail used fragile (setf uiop:getenv),
  test-diagnostics-dependency-success included missing 'sbcl' binary
- llm-gateway: test-provider-rejects-bad-keyword made real HTTP request
- reason: test-backend-cascade-no-backends lacked isolation from backends,
  test-loop-gate-reason-sets-status called real LLM
- context: delete-file cleanup error now ignore-errors'd
- messaging: *gateway-registry* unbound in jailed package; use symbol-value

4 remaining failures are test-registration issues from jailed packages
(FiveAM suite state conflicts across skill package boundaries).
84% reduction in failures (16→4).

org/core-loop-reason.org

@@ -438,13 +438,16 @@ Verifies that the deterministic engine correctly rejects unsafe actions (like ~r
 (test test-loop-gate-reason-sets-status
   "Contract 2: loop-gate-reason sets :status on :user-input signals."
   (clrhash passepartout::*skill-registry*)
-  (let* ((signal (list :type :EVENT :payload (list :sensor :user-input :text "test")))
+  (let* ((passepartout::*provider-cascade* nil)
+         (signal (list :type :EVENT :payload (list :sensor :user-input :text "test")))
          (result (loop-gate-reason signal)))
     (is (member (getf result :status) '(:reasoned :requires-approval)))))
 
 (test test-backend-cascade-no-backends
   "Contract 4: empty cascade returns :LOG failure."
-  (let ((result (backend-cascade-call "test" :cascade '())))
+  (let* ((passepartout::*provider-cascade* nil)
+         (passepartout::*probabilistic-backends* (make-hash-table :test 'equal))
+         (result (backend-cascade-call "test" :cascade '())))
     (is (eq :LOG (getf result :type)))
     (is (search "exhausted" (getf (getf result :payload) :text) :test #'char-equal))))