Live undo/redo: add/delete component and link, move, property edits

Undo and redo now work against a connected device; each step is sent
there through Sox. Deleting a component first reads its whole subtree
back (config, unloaded children, links, place among siblings) so undo
can recreate it; recreated components take new device ids, which the
DOM elements pick up so later steps still reach them. Binary Buf
config (a user's cred) is read with read_prop, since the cache decodes
every Buf as a Str. Moves, tidy layout, and Properties / page editor /
user edits record only what the device accepted.

A step that does not fully reach the device warns and clears the
history. History is also cleared on every view change in live mode,
as opening a sheet rebuilds the DOM from the device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ox_page_view.py

@@ -554,13 +554,19 @@ class OxPageViewPanel:
 
         # Live: the device first, and the page only shows what the device accepted.
         live_failures = []
-        for element, name, _before, after in changes:
+        applied = []
+        for change in changes:
+            element, name, _before, after = change
             if app_state.live_mode and not live_hooks.live_set_prop_value(element, name, after):
                 live_failures.append(f"{name}: {live_hooks.last_error}")
                 continue
             set_prop_value(element, name, after)
+            applied.append(change)
 
-        if not app_state.live_mode:
+        if app_state.live_mode:
+            if applied:
+                undo.push(undo.LiveSlotValueCommand(applied))
+        else:
             undo.push(undo.SlotValueCommand(changes))
         app_state.mark_dirty()