fix: proto-get case-insensitive keyword lookup

proto-get was using getf which does eq comparison, so :EXPLANATION
from the LLM response didn't match :explanation in the policy gate.
Now iterates the plist and compares uppercased strings.

org/core-communication.org

@@ -44,8 +44,12 @@ Returns the value associated with KEY in PLIST by interning a keyword.
 ;; REPL-VERIFIED: 2026-05-03T13:00:00
 #+begin_src lisp
 (defun proto-get (plist key)
-  "Look up KEY in PLIST with keyword normalization."
-  (getf plist (if (keywordp key) key (intern (string-upcase (string key)) :keyword))))
+  "Look up KEY in PLIST with case-insensitive keyword normalization."
+  (let ((key-upcase (string-upcase (string key))))
+    (loop for (k v) on plist by #'cddr
+          when (and (keywordp k)
+                    (string-equal (string k) key-upcase))
+            do (return v))))
 #+end_src
 
 ** Actuator Registry