[codex] Add experimental 0DTE analytics tab

[zifanzhou1024]

Summary

• Add a dedicated experimental analytics tab for 0DTE option-chain research.
• Add price-derived panels for forward center, ATM straddle expected move, risk-neutral distribution/probabilities, skew/tail metrics, move-needed, decay pressure, rich/cheap residuals, and quote-quality checks.
• Add IV smile method comparisons, including a focused OTM midpoint Black-76 vs spline fit chart with hoverable points and method labels.

Why

This gives the experimental page a dense sandbox for comparing 0DTE analytics before deciding which pieces should graduate into the main dashboard.

Validation

• pnpm --filter @gammascope/web test -- tests/ExperimentalDashboard.test.tsx
• pnpm --filter @gammascope/web typecheck
• git diff --check
• Verified the experimental page in the in-app browser at http://127.0.0.1:3003/experimental, including the focused OTM midpoint vs spline chart.