Wires the session's undo/redo into the GUI: ↶ Undo / ↷ Redo toolbar buttons,
add_enabled-gated by can_undo()/can_redo() so they grey out when there is
nothing to do, and Ctrl/Cmd+Z (undo) / Ctrl/Cmd+Shift+Z or Ctrl/Cmd+Y (redo)
shortcuts read with modifier checks (first in handle_keys, so a modified Z is
not also taken as a plain key). A run_history helper handles the
Option-returning steps, reporting "nothing to undo/redo" when the stack is
empty. These run in the toolbar/key path, before the frame's rerender slot, so
there is no stale-texture concern. Module doc, help text, and the crate
description are updated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NAtEiJtt9yKVV1zjKYmZhS
Levi Neuwirth
1496c81302