refactor(ui): centralize physical paint through prof_doupdate()

Upstream's "guard terminal writes while suspended" fix and commit 2 of
this branch both work by sprinkling `if (!isendwin())` (or
`!is_suspended && !isendwin()`) guards around every doupdate() reachable
during a suspended session. That keeps isendwin() a valid signal but
turns the no-stray-write invariant into a whitelist: every new
doupdate / refresh / wrefresh added later in src/ has to remember the
guard, and the original bug class came from exactly such an oversight
in _inp_write.

Introduce a single primitive, prof_doupdate(), that flushes only when
not suspended (via the existing _ui_redraw_suspended() helper). Replace
every direct doupdate() in src/ui/inputwin.c (inp_get_line,
inp_get_password, _inp_write) and the trailing doupdate in ui_update
with the wrapper, collapsing their inline guards. ui_suspend() now
flushes via prof_doupdate() before flipping ui_suspended, so upstream's
pre-endwin flush is preserved.

The flag-based gate in ui_update / ui_resize / ui_redraw is kept as
belt-and-suspenders: even if a future raw doupdate slips in elsewhere,
ui_update has not been refreshing the virtual screen, so the blit finds
stale content rather than a fresh status-bar clock or chat line.

src/ui/core.c

@@ -148,7 +148,7 @@ ui_update(void)
     title_bar_update_virtual();
     status_bar_draw();
     inp_put_back();
-    doupdate();
+    prof_doupdate();
 
     if (perform_resize) {
         perform_resize = FALSE;
@@ -189,9 +189,10 @@ ui_reset_idle_time(void)
 void
 ui_suspend(void)
 {
-    ui_suspended = TRUE;
     inp_suspend();
-    doupdate();
+    // Flush before flipping the flag (prof_doupdate skips while suspended).
+    prof_doupdate();
+    ui_suspended = TRUE;
     endwin();
 }
 
@@ -219,6 +220,14 @@ ui_flash(void)
     }
 }
 
+void
+prof_doupdate(void)
+{
+    if (!_ui_redraw_suspended()) {
+        doupdate();
+    }
+}
+
 void
 ui_resize(void)
 {