Replace the fish `read` prompt (which showed an unstyled `read>` and left the
prompt line behind on redraw) with an in-place editor built on the raw key
reader. The value is edited directly in its UI field with a block caret; the
panel redraws each keystroke and cleans up on exit. Pre-fills the current value;
Backspace deletes, Enter saves (empty reverts to default), Esc cancels.
- __config_settings_read_key: decode Backspace (bytes 8/127)
- __config_settings_draw_value: edit-mode field with caret + edit hint line
- config-settings: inline edit loop replaces the read-based prompt block
rootiest
