get_pixel_dimensions(
timeout_ms) ->win_w,win_h,cell_w,cell_h
Query the terminal for pixel dimensions of the window and cells
Sends CSI 14 t (window pixel size) and CSI 16 t (cell pixel size)
and reads both xterm-style responses. Returns win_w, win_h,
cell_w, cell_h (all in pixels). Returns nil if either response
does not arrive within timeout_ms (default 100 ms) or the terminal
does not support pixel dimension queries.