Pedagogy: add interactive parameter / initial-condition slider to Lorenz attractor notebook

Add an ipywidgets interactive control panel to `50_ode/50_Attractors.ipynb` for the Lorenz system, letting learners vary the parameters (σ, ρ, β) and/or the initial condition `(x₀, y₀, z₀)` and re-render the trajectory in 3D.

## Scope

- Sliders: σ (e.g., 0–20), ρ (e.g., 0–60, with 28 highlighted as the canonical chaotic value), β (e.g., 0–4).
- Optional: 3 sliders for initial condition.
- Re-integrate with `scipy.integrate.solve_ivp` on slider change and redraw the 3D phase plot.

## Why

The Lorenz attractor's whole pedagogical hook is sensitivity to parameters and initial conditions — the *bifurcation* from a stable point to chaos as ρ crosses ~24.74, the well-known butterfly emerging at ρ=28. A static plot conveys none of that. An interactive scrubber lets learners discover the structure themselves, which is the entire point of teaching chaos numerically.

Start with 50_ode/50_Attractors.ipynb and run the existing Lorenz attractor notebook to understand its current integration and 3D plot. Add an ipywidgets control panel for the Lorenz parameters and, optionally, initial conditions, re-integrating with scipy.integrate.solve_ivp on changes. Done means learners can vary the values and see the trajectory update in 3D.

Written by the indexing model from the issue text.