docs: create comprehensive documentation and deep-dive examples

- Created DOCUMENTATION.md covering core philosophy, modules, and platform specifics.
- Created EXAMPLES_FULL.md with complex multi-platform usage scenarios.
- Updated README.md and docs/index.md to centralize documentation links.

EXAMPLES_FULL.md

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+# Entropyk: Comprehensive Examples
+
+This document provides deep-dive examples for various Entropyk features across different platforms.
+
+## 1. Simple Refrigeration Cycle (Rust)
+The "Hello World" of thermodynamics.
+
+```rust
+use entropyk_components::compressor::{Compressor, Ahri540Coefficients};
+use entropyk_components::heat_exchanger::{Condenser, Evaporator};
+use entropyk_components::expansion_valve::ExpansionValve;
+use entropyk_solver::{System, FallbackConfig};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut system = System::new();
+
+    // 1. Create Components
+    let comp = Compressor::new(Ahri540Coefficients::typical(), ...)?;
+    let cond = Condenser::new(5000.0);
+    let valve = ExpansionValve::new(...)?;
+    let evap = Evaporator::new(3000.0);
+
+    // 2. Add to System & Connect
+    let n1 = system.add_component(Box::new(comp));
+    let n2 = system.add_component(Box::new(cond));
+    let n3 = system.add_component(Box::new(valve));
+    let n4 = system.add_component(Box::new(evap));
+
+    system.add_edge(n1, n2)?; // Comp -> Cond
+    system.add_edge(n2, n3)?; // Cond -> Valve
+    system.add_edge(n3, n4)?; // Valve -> Evap
+    system.add_edge(n4, n1)?; // Evap -> Comp
+
+    // 3. Finalize & Solve
+    system.finalize()?;
+    let config = FallbackConfig::default();
+    let result = config.solve(&system)?;
+
+    println!("Cycle COP: {}", result.cop());
+    Ok(())
+}
+```
+
+## 2. Parameter Estimation in Python
+Estimating fouling (UA reduction) from sensor data.
+
+```python
+import entropyk as ek
+
+# Setup system with experimental targets
+system = ek.System()
+comp = system.add_component(ek.Compressor(...))
+cond = system.add_component(ek.Condenser(ua=5000.0)) # Initial guess
+
+# Add Inverse Control target: Discharge temperature must match sensor
+system.add_constraint(target_node=cond, target_value=325.15, ... )
+
+# Solve for the UA that makes the physics match the sensor
+solver = ek.NewtonConfig(inverse_mode=True)
+result = solver.solve(system)
+
+print(f"Calculated UA: {result.component_params[cond].ua} W/K")
+```
+
+## 3. Custom Component Implementation
+How to add a new physical model.
+
+```rust
+use entropyk_components::{Component, SystemState, ResidualVector, JacobianBuilder, ConnectedPort};
+
+struct BypassValve {
+    opening: f64,
+}
+
+impl Component for BypassValve {
+    fn compute_residuals(&self, state: &SystemState, residuals: &mut ResidualVector) -> Result<(), ComponentError> {
+        // P_out = P_in - (k * opening^2 * flow^2)
+        residuals[0] = state[1] - (state[0] - self.calc_dp(state));
+        Ok(())
+    }
+
+    fn jacobian_entries(&self, state: &SystemState, jacobian: &mut JacobianBuilder) -> Result<(), ComponentError> {
+        // Provide partial derivatives for fast convergence
+        jacobian.add_entry(0, 0, self.dp_dm(state));
+        jacobian.add_entry(0, 1, 1.0);
+        Ok(())
+    }
+
+    fn n_equations(&self) -> usize { 1 }
+    fn get_ports(&self) -> &[ConnectedPort] { &self.ports }
+}
+```
+
+## 4. Multi-Circuit Coupling
+Bridging a Chiller to a Water loop.
+
+```rust
+// Evaporator acts as a bridge
+let evaporator = HeatExchanger::new_bridge(ua);
+
+system.add_edge(refrigerant_valve, evaporator.side_a_in)?;
+system.add_edge(evaporator.side_a_out, refrigerant_comp)?;
+
+system.add_edge(water_pump, evaporator.side_b_in)?;
+system.add_edge(evaporator.side_b_out, water_building)?;
+```