v0.7.2: undo/redo — TDD

Operation-level memory undo/redo built on existing Merkle snapshot
infrastructure. undo-snapshot captures state before destructive tool
execution. /undo and /redo TUI commands send structured events.

- core-memory: undo-snapshot, undo, redo functions + 3 tests
- core-perceive: :undo/:redo sensor handlers
- core-act: auto-snapshot before non-read-only tools
- core-package: undo/redo symbol exports
- channel-tui-main: /undo, /redo commands + 2 tests
- Core: 73/73  TUI Main: 74/74

lisp/channel-tui-main.lisp

@@ -97,7 +97,14 @@
                 (setf (st :input-hpos) 0)
                 (setf (st :scroll-offset) 0)
                 (cond
-                  ;; v0.7.2: HITL inline — structured approval/denial
+                  ;; v0.7.2: undo/redo
+                  ((string-equal text "/undo")
+                   (send-daemon (list :type :event :payload (list :sensor :undo)))
+                   (add-msg :system "Undo: restoring memory to previous state"))
+                  ((string-equal text "/redo")
+                   (send-daemon (list :type :event :payload (list :sensor :redo)))
+                   (add-msg :system "Redo: restoring memory"))
+                  ;; /help command
                   ((and (>= (length text) 9)
                         (string-equal (subseq text 0 9) "/approve "))
                    (let ((token (string-trim '(#\Space) (subseq text 9))))
@@ -797,3 +804,25 @@
   (let ((m (aref (st :messages) 0)))
     (fiveam:is (eq :system (getf m :role)))
     (fiveam:is (search "Denied" (getf m :content)))))
+
+;; ── v0.7.2 Undo/Redo ──
+
+(fiveam:test test-undo-command
+  "Contract v0.7.2: /undo sends undo event."
+  (init-state)
+  (dolist (ch (coerce "/undo" 'list))
+    (on-key (char-code ch)))
+  (on-key 343)
+  (let ((m (aref (st :messages) 0)))
+    (fiveam:is (eq :system (getf m :role)))
+    (fiveam:is (search "Undo" (getf m :content)))))
+
+(fiveam:test test-redo-command
+  "Contract v0.7.2: /redo sends redo event."
+  (init-state)
+  (dolist (ch (coerce "/redo" 'list))
+    (on-key (char-code ch)))
+  (on-key 343)
+  (let ((m (aref (st :messages) 0)))
+    (fiveam:is (eq :system (getf m :role)))
+    (fiveam:is (search "Redo" (getf m :content)))))