Address CodeRabbit review on #3307: the new `Seq::Erase` arm discarded
the `tool_key` Result, dropping an erase error silently, whereas the
old `route_type_input`/`text_key` path reported it via `app.status`.
Mirror that behaviour so a failed Backspace/Delete still surfaces in
the status bar. Behaviour otherwise unchanged; fmt/clippy clean and the
three IME tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Hook IMEs recompose by injecting Backspace key events and VK_PACKET
characters, which egui surfaces as interleaved Event::Text and
Event::Key(Backspace) in one frame. type_text handled text/IME in one
pass and left Backspace to a later pass, so within a frame all text was
inserted before any delete and the diacritics were eaten (tiếng -> tieng).
Take Text, IME and plain Backspace/Delete in a single event-ordered pass,
removing handled keys so route_type_input does not repeat them. Modified
keys and composing frames are unchanged. Adds two canvas IME tests.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
