ime: Reset terminal's IME state on text_input.leave

To reproduce issue:
- Launch an IME from inside foot
- Type in some preedit text
- Use Ctrl-C to close the IME
- IME text stays in terminal until focus is changed

ime.c

@@ -39,6 +39,11 @@ leave(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
 {
     struct seat *seat = data;
     LOG_DBG("leave: seat=%s", seat->name);
+
+    struct terminal *term = seat->kbd_focus;
+    if (term != NULL)
+        term_ime_reset(term);
+
     ime_disable(seat);
 }