Add Ti64 and diamond phonon benchmarks

[7radians]

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Summary

This PR adds two new bulk-crystal phonon benchmarks with Dash app integration:

Ti-6Al-4V (Ti64) phonons (bulk_crystal/ti64_phonons)

• Calc: Runs a CASTEP-referenced phonon suite across 10 Ti64 configurations (hcp/hex + bcc variants). For each model/case it relaxes the structure (LBFGS) then computes:
  • dispersion on a high-symmetry k-path,
  • DOS/PDOS on a dense mesh,
  • optional thermo/free-energy curves for a defined subset of cases.
    Raw outputs are written to outputs/<model>/ as <case>.npz + <case>.json.
• Analysis: Produces per-model metrics.json plus:
  • ti64_phonons_metrics_table.json (Dash table)
  • ti64_phonons_interactive.json (interactive scatter)
    Metrics include dispersion RMSE (mean/max), ω_avg MAE, and ΔF per-atom at 0 K / 2000 K for TP-enabled cases.
• App: Adds a Dash app that reuses shared callback builders to provide:
  • table → ω_avg scatter (ref vs pred),
  • scatter selection → rendered dispersion + DOS preview from calc artifacts.

Diamond phonons (bands-only) (bulk_crystal/diamond_phonons)

• Calc: Computes phonopy force constants and band dispersions for diamond for each model and writes FORCE_CONSTANTS + band.yaml under outputs/<model>/. The phonon band path is taken directly from the DFT reference NPZ (dft_band.npz) so predictions match the exact reference q-path.
• Analysis: Loads the DFT reference bands (cm⁻¹ → THz), loads each model’s band.yaml, sorts bands per q-point and reports Band MAE + Band RMSE (THz). Writes:
  • diamond_phonons_bands_table.json
  • diamond_phonons_bands_interactive.json
• App: Adds a Dash app that shows metric scatter plots and a per-model dispersion preview panel rendered from band.yaml with optional DFT overlay (RSCAN).

Linked issue

Resolves #297

Progress

• Calculations
• Analysis
• Application
• Documentation

Testing

Tested both benchmarks on:

• mace-mp-0a
• mace-mp-0b3
• mace-mpa-0
• mace-omat-0
• mace-matpes-r2scan
• orb-v3-consv-inf-omat
• pet-mad

New decorators/callbacks

• No new callbacks/decorators required (reuses existing table/scatter decorators and shared callback builders).