term/osk: scroll region so the OSK never hides the input line

The terminal now has a variable usable height (wTermRows). term_scroll and
cursor_down operate within [0 .. wTermRows-1], and term_set_rows(n) shrinks
or grows that region, scrolling the cursor up into view when it would fall
outside. osk_toggle shrinks the terminal to the rows above the keyboard on
show (18 - OSK_ROWS = 15) and restores full height on hide, so the active
line is always visible just above the docked keyboard, and hiding the OSK
reclaims all 18 rows.

Also add c/count.c ("count [n]", default 25): prints n numbered lines to
observe/debug scrolling and the scroll-region behavior. Registered as
program id 21 / bank 23. Fixed the arg to read argv[0] (getargs returns the
string after the command name).

Verified: filling the screen then opening the OSK scrolls the latest line
to row 14 (visible) with the keyboard at 15-17; closing it restores rows
15-17; count N prints exactly N lines.

1 files changed, 16 insertions, 0 deletions

diff --git a/c/count.c b/c/count.c
new file mode 100644
index 0000000..37cdcce
--- /dev/null
+++ b/c/count.c
@@ -0,0 +1,16 @@
+#include "gbos.h"
+/* count [n]: print n numbered lines (default 25) to observe terminal scrolling
+   and the OSK scroll-region. Each line is tagged so you can tell which lines
+   are visible after scrolling. */
+void main(void) {
+    char *argv[4];
+    unsigned char argc = argv_parse(argv, 4);
+    unsigned char n = 25, i;
+    if (argc >= 1) n = atou(argv[0]);
+    for (i = 1; i <= n; i++) {
+        puts("line ");
+        putu(i);
+        puts(" ------------------");
+        nl();
+    }
+}