Add multi-frequency waveform inversion script with GT comparison and GIF output

[Fuwsusu]

Motivation

• Provide a self-contained MATLAB script that performs multi-frequency waveform inversion with options to compare against Ali-512 reference results or a GIF-based image reference.
• Enable per-iteration visualization via GIF output and produce quantitative metrics and saved reconstruction results for later analysis.

Description

• Add new script FuWs/MultiFrequencyWaveformInvKCI_fws20260414_compareTrue.m that loads sample data, constructs a DTFT-based frequency dataset, windows time traces, and applies a phase-screen correction and outlier removal.
• Implement an iterative Helmholtz-based inversion loop using a conjugate-gradient approach across frequencies with separate sound-speed (SoS) and attenuation updates, virtual sources, ringing removal via ringingRemovalFilt, and forward/adjoint solves via HelmholtzSolver.
• Add ground-truth discovery logic to automatically locate Ali-512 datasets or use the last frame of a provided GIF as image-domain truth, compute quantitative metrics (PSNR, RMSE, SSIM, RD) for either physical or image-domain references, and save the iteration history to a results .mat file.
• Add iterative GIF generation and preview support, iteration control flags (runAllIterations, requestedIterations), and a small helper ternary function used for display labels.

Testing

• No automated tests were executed as part of this change.

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Codex Task