fix: harden p/u validation and Hotelling simulation

[flaviobarros]

Summary

Closes #97. Hardens the scientific validation merged in #93, #95 and #96.

Changes

Reusable validation evidence

• adds inst/extdata/validation/p_chart_joekes_barbosa_2013.csv;
• adds inst/extdata/validation/u_chart_cf_derivation.csv;
• separates published-table reproduction from independent derivation;
• makes the fixtures reusable by the future numerical-validation vignette ([P1][DOC] Criar vignette consolidada de validação científica do IQCC #91).

p chart

• replaces circular nUCL = n * published_UCL checks with n * oracle_UCL;
• records tolerance ratios from independently calculated limits;
• distinguishes risk reproduced from rounded table limits from risk computed with unrounded production limits.

u chart

• replaces the truncated Poisson sum with exact ppois() tails;
• evaluates the CF2 second-order correction at the signed lower quantile for the LCL;
• documents and tests both three-sigma tail formulas;
• adds a regression test against the former same-sign LCL convention.

Hotelling T² simulation

• factors the elliptical multivariate-t sampler into an internal testable helper;
• tests that one radial chi-square factor is shared across components of each observation;
• tests approximate covariance scaling;
• replaces the chi-square-density MCSE with an empirical order-statistic spacing estimate;
• preserves the public return structure.

CI/documentation

• synchronizes generated Rd files;
• extends inst/WORDLIST for the Hotelling terminology that was leaving documentation-quality red.

Review notes

The u-chart CF2 LCL changes numerically for non-truncated two-sided cases. This is intentional: the lower-tail Cornish-Fisher expansion must be evaluated at z_lower < 0; the previous implementation reused the upper-tail second-order adjustment.

No merge, tag or release action is requested automatically.

[flaviobarros]

Revisão científica e de integração concluída. Confirmei: fixtures reutilizáveis e não circulares para p; caudas Poisson exatas e LCL CF2 avaliada no quantil inferior assinado para u; MCSE empírico e gerador t elíptico testável para Hotelling T²; documentação sincronizada; todos os workflows verdes em Linux, macOS e Windows. Não encontrei bloqueadores para integração.