fix(ui): reserve pad height per message to prevent multi-line clip and scroll desync

A tall multi-line message printed near the bottom of the ncurses pad was clipped because _win_print_internal grew the pad from the current cursor only (_win_ensure_pad_capacity(getcury)), not the height of the message about to be printed. The clipped message's captured height (e.g. 1 row for a 49-row message) was wrong while win_redraw later rendered it in full; the resulting buffer->lines / y_start_pos mismatch desynced the page-up scroll anchor, producing a ~one-page jump when scrolling past such messages from history.

Estimate the rendered height (hard newlines + soft-wrap over the usable width) and reserve that many rows before printing, so the message is never clipped and its captured height matches the redraw. All print paths go through _win_print_internal, so incoming/outgoing/history are covered.

Regression from the upstream sync (72f4f186d), which replaced the fixed-size pad with the dynamic _win_ensure_pad_capacity model.

src/ui/window.c

@@ -72,7 +72,10 @@ _win_ensure_pad_capacity(ProfWin* window, WINDOW* win, int lines_needed)
 static int
 _win_estimated_lines(WINDOW* win, const char* const message, int indent, int pad_indent)
 {
-    int usable = MAX(1, getmaxx(win) - (indent + pad_indent));
+    int usable = getmaxx(win) - (indent + pad_indent);
+    if (usable < 1) {
+        usable = 1;
+    }
     int newlines = 0;
     for (const char* p = message; *p; p++) {
         if (*p == '\n') {