Feat: Implement interconnected organ simulation

This commit refactors the organ simulation to enable dynamic interactions between organs, replacing the previous "faked" or hardcoded connections.

Key changes include:
- Major Refactoring: Changed the `Organ::update` method signature to `update(Patient& patient, double deltaTime_s)`, allowing organs to access the shared patient state and other organs. This was propagated to all organ classes.
- Blood Chemistry Model: Introduced a central `Blood` struct in the `Patient` model to track shared resources like oxygen, CO2, glucose, and toxins.
- Organ System Interconnections:
    - Lungs & Brain: Lungs now perform gas exchange affecting the blood. The brain consumes O2, produces CO2, and its GCS is affected by hypoxia/hypercapnia.
    - Liver-Gallbladder: Gallbladder now receives bile directly from the liver's production rate.
    - Digestive System: Stomach passes chyme to the intestines, which absorb glucose into the blood. The pancreas responds to blood glucose changes.
    - Renal System: Kidneys' GFR is now influenced by the heart's aortic pressure, and they produce urine that fills the bladder directly.
    - Cardiovascular & Neurological: The heart rate responds to hypoxia, and the brain uses live aortic pressure from the heart.
- Comprehensive Test Scenario: Updated the main example to include a 60-second simulation with a meal and a lung injury event to verify the new interconnected system.

This creates a more realistic and scalable physiological simulation framework where organ behaviors are emergent from their interactions.

src/Intestines.cpp

@@ -1,4 +1,5 @@
 #include "MedicalLib/Intestines.h"
+#include "MedicalLib/Patient.h"
 #include <random>
 #include <algorithm>
 #include <sstream>
@@ -23,20 +24,16 @@ Intestines::Intestines(int id)
     colon = {"Colon", 1.5, 0.5, 0.1, 1.0}; // High water absorption
 }
 
-void Intestines::update(double deltaTime_s) {
-    // For demonstration, simulate chyme arriving from the stomach
-    static double timeSinceChyme = 0.0;
-    timeSinceChyme += deltaTime_s;
-    if (timeSinceChyme > 25.0) {
-        receiveChyme(10.0); // Receive 10mL of chyme
-        timeSinceChyme = 0.0;
-    }
-
+void Intestines::update(Patient& patient, double deltaTime_s) {
     if (chymeVolume_mL > 0) {
         // Simplified absorption model: total absorption is an average of all segments
         double totalNutrientAbsorption = (duodenum.nutrientAbsorptionRate + jejunum.nutrientAbsorptionRate + ileum.nutrientAbsorptionRate + colon.nutrientAbsorptionRate) / 4.0;
         double totalWaterAbsorption = (duodenum.waterAbsorptionRate + jejunum.waterAbsorptionRate + ileum.waterAbsorptionRate + colon.waterAbsorptionRate) / 4.0;
 
+        // Absorb glucose into the blood
+        double glucoseAbsorption = totalNutrientAbsorption * chymeVolume_mL * 0.001 * deltaTime_s;
+        patient.blood.glucose_mg_per_dL += glucoseAbsorption;
+
         // Reduce chyme volume based on absorption
         double absorbedVolume = (totalNutrientAbsorption * 0.01 + totalWaterAbsorption * 0.1) * deltaTime_s;
         chymeVolume_mL -= absorbedVolume;