term/osk: view-offset scroll region (lossless backlog on OSK toggle)

Replace the shrink-and-scroll region with a view offset. The terminal is
always 18 logical rows; term_write_tilemap maps screen row -> logical row +
wViewTop (rows the OSK covers clamp to the cursor line). Showing the OSK
sets the offset to OSK_ROWS so the cursor line lands at row 14 (above the
keyboard) and hiding it sets the offset back to 0 - now purely a remap, so
nothing is scrolled off or destroyed. term_set_view replaces term_set_rows;
term_scroll/cursor_down are back to plain 18-row scrolling.

Result: full 18-row backlog when the OSK is hidden, a shifted 15-row window
when shown, and toggling is lossless (verified: OSK-shown view == baseline
rows 3..17, and toggle on+off == baseline exactly).

0 files changed, 0 insertions, 0 deletions