fix(ui): reclaim pad by dead space instead of absolute height

Variant A (PAD_THRESHOLD=12000) bounds the pad but still re-enters win_redraw() from the print path on every message once the *live* buffer renders >= the threshold — reachable with a single oversized message (huge paste, narrow terminal, crafted incoming), reintroducing the per-message redraw storm.

Trigger the reclaim redraw on dead space (getcury - buffer->lines) instead of absolute pad height. After a redraw the cursor equals buffer->lines, so dead space is 0 regardless of buffer size: the reclaim can never fire while scrolling, and an oversized message no longer storms (and is shown in full rather than clipped). Dead space only accrues in a long append-only session that trimmed old entries — exactly when reclaiming is wanted.

src/ui/window.c

@@ -43,7 +43,7 @@
 #include "ai/ai_client.h"
 
 static const int PAD_MIN_HEIGHT = 100;
-static const int PAD_THRESHOLD = 12000; // above buffer cap (~9000): reclaims dead pad space, never fires while scrolling
+static const int PAD_DEAD_SPACE_LIMIT = 2000; // reclaim once the pad holds this much dead space (cursor past live buffer); size-independent, so it never fires while scrolling
 static gboolean _in_redraw = FALSE;
 
 static void
@@ -56,9 +56,10 @@ _win_ensure_pad_capacity(ProfWin* window, WINDOW* win, int lines_needed)
     int cur_height = getmaxy(win);
     int cur_width = getmaxx(win);
     if (lines_needed >= cur_height - 1) {
-        // If we are getting too large, trigger a redraw to clean up old lines
-        // but only if we are not already in a redraw process.
-        if (window && cur_height >= PAD_THRESHOLD && !_in_redraw) {
+        // redraw to reclaim dead pad space (cursor far past live buffer, e.g. a long
+        // append-only session); dead space never accrues while scrolling, only here
+        int dead = window ? lines_needed - window->layout->buffer->lines : 0;
+        if (window && dead > PAD_DEAD_SPACE_LIMIT && !_in_redraw) {
             win_redraw(window);
         } else {
             // resize to required lines + some buffer for next messages
@@ -67,6 +68,20 @@ _win_ensure_pad_capacity(ProfWin* window, WINDOW* win, int lines_needed)
         }
     }
 }
+
+// upper-bound estimate of rows a message body occupies (hard newlines + soft-wrap), to reserve pad space before printing so a tall message isn't clipped (a clipped height desyncs the scroll offset)
+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 newlines = 0;
+    for (const char* p = message; *p; p++) {
+        if (*p == '\n') {
+            newlines++;
+        }
+    }
+    return newlines + utf8_display_len(message) / usable + 2;
+}
 static const char* LOADING_MESSAGE = "Loading older messages…";
 static const char* CONS_WIN_TITLE = "CProof. Type /help for help information.";
 static const char* XML_WIN_TITLE = "XML Console";
@@ -2001,7 +2016,7 @@ _win_print_internal(ProfWin* window, const char* show_char, int pad_indent, GDat
         }
     }
 
-    _win_ensure_pad_capacity(window, window->layout->win, getcury(window->layout->win));
+    _win_ensure_pad_capacity(window, window->layout->win, getcury(window->layout->win) + _win_estimated_lines(window->layout->win, message + offset, indent, pad_indent));
 
     if (prefs_get_boolean(PREF_WRAP)) {
         _win_print_wrapped(window->layout->win, message + offset, indent, pad_indent);