qp_lvgl_flush() called lv_disp_flush_ready() only inside the
`if (selected_display)` block. When LVGL invokes the flush callback while
selected_display is NULL, the callback returns without ever signalling
completion, so LVGL keeps the flush marked "in progress" and stalls all
further rendering.
Move lv_disp_flush_ready() out of the conditional so it is always called,
per LVGL's contract that every flush_cb must signal ready exactly once.
cancel_key_lock() called UNSET_KEY_STATE(0x0), which expands to clearing
only bit 0 of key_state[0]. The lock state is a 256-bit map spread across
key_state[0..3], so every locked key other than keycode 0x00 stayed
latched after a cancel.
Zero all four words so cancel_key_lock() releases every locked key, as
its name and its public declaration in process_key_lock.h imply.
Arca Artem