fix(ui): address PR review on WIN_CHAT scroll handling

- Drop DB_RESPONSE_ERROR -> REACHED_BOTTOM in win_page_down: a transient
  backend error (e.g. sqlite lock) should not force the scroll state
  forward, or the user would get stuck mid-conversation expecting more
  rows that did not load.
- Trim the _win_printf comment to a single WHY line; the rest belongs in
  the originating commit message.

src/ui/window.c

@@ -813,9 +813,7 @@ win_page_down(ProfWin* window, int scroll_size)
             auto_gchar gchar* start = g_date_time_format_iso8601(last_entry->time);
             auto_gchar gchar* end_date = g_date_time_format_iso8601(now);
             db_history_result_t db_response = chatwin_db_history((ProfChatWin*)window, start, end_date, FALSE);
-            // Treat transient DB error (e.g. no active backend) the same
-            // as EMPTY: no rows can be fetched, so stop indicating [SCROLLED].
-            if (db_response == DB_RESPONSE_EMPTY || db_response == DB_RESPONSE_ERROR)
+            if (db_response == DB_RESPONSE_EMPTY)
                 *scroll_state = WIN_SCROLL_REACHED_BOTTOM;
 
             // similar to page_up (see explanation there)
@@ -1811,13 +1809,9 @@ static void
 _win_printf(ProfWin* window, const char* show_char, int pad_indent, GDateTime* timestamp, int flags, theme_item_t theme_item, const char* const display_from, const char* const from_jid, const char* const message_id, const char* const message, ...)
 {
 
-    /* While the user is scrolled, bump the unread indicator. WIN_CHAT
-     * skips the buffer/render only when the DB will preserve the message
-     * verbatim — chatwin_db_history on scroll-down will replay it. When
-     * the DB is off/redact/dead we cannot recover, so fall through and
-     * append to the buffer just like non-chat windows. */
     if (window->layout->paged && wins_is_current(window)) {
         window->layout->unread_msg++;
+        // Skip buffer only when DB can replay the message on scroll-down.
         if (window->type == WIN_CHAT && log_database_can_recover_messages()) {
             return;
         }