_win_printf used to drop the buffer append and pad render for any window
in paged state, but only WIN_CHAT can recover lost messages via
chatwin_db_history on scroll-down. WIN_MUC, WIN_PRIVATE and WIN_AI have
no such fallback, so incoming and outgoing messages were silently lost
when the user was viewing history. Suppress the buffer/render only for
WIN_CHAT; for the rest, still bump unread_msg but let the message land
in the buffer so it becomes visible on scroll-down.

This also removes the manual paged/unread_msg reset before printing the
user message in cl_ev_send_ai_msg — it was a local workaround for the
same drop and is no longer needed.

The buffer-bottom reset in win_page_down (c167f487) is still required:
it is the only path that clears paged and unread_msg for non-chat
windows when the user scrolls back to the bottom (WIN_SCROLL_REACHED_BOTTOM
is set only on the is_chat DB branch).

@@ -816,1 +816,3 @@
-            if (db_response == DB_RESPONSE_EMPTY)
+            // 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)

@@ -1805,0 +1815,4 @@
+     * 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. */