⚙️ Core: Stencil Pattern for TuringSystem

[fderuiter]

Refactored math_explorer/src/biology/morphogenesis.rs to eliminate DRY violation in TuringSystem.
Extracted the finite-difference stencil and reaction logic into apply_stencil_impl.
Verified with tests.
Updated engineering decision records.

---

PR created automatically by Jules for task 16301892021858618432 started by @fderuiter

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[fderuiter]

Run cargo fmt -- --check
Diff in /home/runner/work/math/math/math_explorer/src/biology/morphogenesis.rs:256:
&self.state,
&mut self.next_state.u,
&mut self.next_state.v,

•        |u_curr, v_curr, du_dt, dv_dt| {
  

•            (
  

•                u_curr + dt * du_dt,
  

•                v_curr + dt * dv_dt,
  

•            )
  

•        },
  

•        |u_curr, v_curr, du_dt, dv_dt| (u_curr + dt * du_dt, v_curr + dt * dv_dt),
     );
  
     // Swap buffers (states)
  

Diff in /home/runner/work/math/math/math_explorer/src/biology/morphogenesis.rs:281:
input_state: &TuringState,
out_u: &mut [f64],
out_v: &mut [f64],

•    mut op: F
  

• )
• where

•    mut op: F,
  

• ) where
  F: FnMut(f64, f64, f64, f64) -> (f64, f64),
  {
  let n = input_state.len();
  Error: Process completed with exit code 1.

[google-labs-jules]

Run cargo fmt -- --check
Diff in /home/runner/work/math/math/math_explorer/src/biology/morphogenesis.rs:256:
&self.state,
&mut self.next_state.u,
&mut self.next_state.v,

•        |u_curr, v_curr, du_dt, dv_dt| {
  

•            (
  

•                u_curr + dt * du_dt,
  

•                v_curr + dt * dv_dt,
  

•            )
  

•        },
  

•        |u_curr, v_curr, du_dt, dv_dt| (u_curr + dt * du_dt, v_curr + dt * dv_dt),
     );
  
     // Swap buffers (states)
  

Diff in /home/runner/work/math/math/math_explorer/src/biology/morphogenesis.rs:281:
input_state: &TuringState,
out_u: &mut [f64],
out_v: &mut [f64],

•    mut op: F
  

• )
• where

•    mut op: F,
  

• ) where
  F: FnMut(f64, f64, f64, f64) -> (f64, f64),
  {
  let n = input_state.len();
  Error: Process completed with exit code 1.

Fixed formatting as requested by running cargo fmt.