GUI: add on-screen toasts and atomic config writes

- Toast queue drawn in the top-right by the overlay, independent of the GUI
  being open. Info/warn/error colors and 6/9/12 s lifetimes; timers start on
  the first painted frame so startup messages are not missed.
- Queue a load toast after install_menu, plus warnings/errors for missing
  modules/interfaces/netvars, input hooks, fonts, ISurface, server datamap,
  and spread seed support.
- Toast on config reload, reset, bind/unbind and config save failure.
- Config saves now write `config.tmp`, flush, then rename it over the real
  file; failures leave the previous config intact.
- config_load reports whether a file was found so Reload can distinguish a
  successful reload from a missing file.
- Update CONTEXT and ISURFACE_STATUS for the single GUI, toasts and atomic
  config writes.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/server.cpp b/src/server.cpp
index 896ce3e..cfb4dd1 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -123,6 +123,7 @@ bool resolve_server_netvars() {
     fail_logged = true;
     logf("server datamap: scan failed (server.so at %s)",
          g_server.path.c_str());
+    toastf(TOAST_WARN, "Server datamap scan failed; jumpbug assist limited");
   }
   return g_srv_ready;
 }