🛰️ GPS Trilateration (2D): Least-Squares Fix & Dilution of Precision

This 2D companion strips GPS positioning down to its two-unknown core: 3-8 satellites at known positions each report a distance measurement corrupted by real Gaussian range noise, and the receiver's position is recovered the same way a real receiver recovers it — by Gauss-Newton least squares on the range-residual equations, not by eyeballing where circles cross. A live scatter cloud of repeated fixes and a theoretical covariance ellipse make dilution of precision directly visible: spreading the satellites across the sky keeps the fix tight for a given noise level, while cramming them into a narrow arc inflates the same noise into a much larger position error.