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/core-perceive.lisp

@@ -89,8 +89,15 @@ FN receives (signal) and returns T if consumed, nil to continue."
                    (snapshot-memory)
                    (setf *loop-focus-id* (getf element :id))
                    (ingest-ast element :scope (if *scope-resolver* (funcall *scope-resolver*) :memex)))))
-              (:interrupt
-               (setf *loop-interrupt* t))
+               (:interrupt
+                (setf *loop-interrupt* t))
+               ;; v0.7.2 undo/redo
+               (:undo
+                (log-message "GATE [Perceive]: undo requested")
+                (undo "perceive"))
+               (:redo
+                (log-message "GATE [Perceive]: redo requested")
+                (redo "perceive"))
               ;; HITL: re-injected approved action from dispatcher-approvals-process
               (:approval-required
                (when (getf payload :approved)