refactor(core/rendering): nomenar constants a RenderInfo (HC-06/-07/-09 + PATCH-08)

render_info.cpp tenia diverses "cifres soltes" amb significat
estructural:
- Índex 0/1/2/3 dins segments_ per a FPS/driver/shader/temps — ara
  FPS_SEGMENT, DRIVER_SEGMENT, SHADER_SEGMENT, TIME_SEGMENT (HC-06).
- +1,+1 per a la ombra del text — ara SHADOW_OFFSET_PX (HC-09).
- % 3 al cicle de posicions de global_inputs.cpp — ara
  Defaults::RENDER_INFO_POSITION_COUNT (HC-07).

A més, init() assignava mono_digits=true al segment de temps que
refreshSegments() ja marca a cada crida, inclosa la primera d'update()
abans de render. S'elimina el doblegat (PATCH-08); el comentari
explica la garantia.

Build + smoke 5s xvfb OK (exit 124).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

source/core/input/global_inputs.cpp

@@ -139,7 +139,7 @@ namespace GlobalInputs {
         }
 
         void onCycleRenderInfo() {
-            const int NEXT = (static_cast<int>(Options::video.render_info_position) + 1) % 3;
+            const int NEXT = (static_cast<int>(Options::video.render_info_position) + 1) % Defaults::RENDER_INFO_POSITION_COUNT;
             Options::video.render_info_position = static_cast<Defaults::RenderInfoPosition>(NEXT);
             Options::saveToFile();
         }