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>

properties.py

@@ -1170,7 +1170,9 @@ class PropertiesPanel:
         # In live mode the device is written first and a value only lands in the document
         # once the device took it, so the panel never shows what the device does not hold.
         live_failures = []
-        for element, prop_name, before, after in changes:
+        applied = []
+        for change in changes:
+            element, prop_name, before, after = change
             if app_state.live_mode and not live_hooks.live_set_prop_value(
                     element, prop_name, after):
                 live_failures.append(f"{prop_name}: {live_hooks.last_error}")
@@ -1182,9 +1184,14 @@ class PropertiesPanel:
                 continue
             if prop_name != "meta":
                 set_prop_value(element, prop_name, after)
-        written = len(changes) - len(live_failures)
+            applied.append(change)
+        written = len(applied)
 
-        if not app_state.live_mode:
+        if app_state.live_mode:
+            # Only what the device took; undo writes it back there.
+            if applied:
+                undo.push(undo.LiveSlotValueCommand(applied))
+        else:
             undo.push(undo.SlotValueCommand(list(changes)))
         app_state.mark_dirty()