Function init

init(
    rule:
        | ((t: number, y: number) => number)
        | ((t: number, y: number, dy: number) => number)
        | ((t: number, y: number[]) => number[]),
    dimension?: number,
): ChalkboardODE
Defines an ordinary differential equation.
Parameters
- rule:
      | ((t: number, y: number) => number)
      | ((t: number, y: number, dy: number) => number)
      | ((t: number, y: number[]) => number[])
  The differential equation rule function.
- Optionaldimension: number
  Optional, the dimension of the system only required for system equations.
Returns ChalkboardODE
Example
```
// First-order scalar ODE: y' = -2y
const ode1 = Chalkboard.diff.init((t, y) => -2 * y);

// Second-order scalar ODE: y'' = -y  (harmonic oscillator)
const ode2 = Chalkboard.diff.init((t, y, dy) => -y);

// System ODE: dy/dt = [y2, -y1]  (2D system)
const odeSys = Chalkboard.diff.init((t, y) => [y[1], -y[0]], 2);
```
- Defined in Chalkboard.diff.ts:300