PRISM-US-MH-0.5: daily estimation

PRISM-US-MH-0.5 — estimation switches from weekly to daily returns (weekly formation, daily regressions): ~10× the covariance effective observations (252d correlation half-life ≈ 730 obs). Measured: Mincer–Zarnowitz slope 0.81→1.02, min-var optimized-portfolio bias 1.36→1.09 (matching Shepard's 1/(1−K/N_eff)), ETF bias statistics 0.87–1.08. Also ships: optimized=true Shepard correction flag (Python + MCP), per-factor WLS t-statistics (factor_tstats.parquet + /model.md quality table), daily ETF RBSA. Cold rebuild (weekly history incommensurable). 2,987 covered / 2,774 estimation / 713 daily regressions over 149 weeks.