causalfrag 0.1.0

• Initial CRAN submission.
• Introduces the Causal Fragility Index (CFI): a 0-100 composite score integrating sensitivity evidence across frameworks.
• run_sensitivity() – unified dispatch to sensemakr, EValue, konfound.
• flag_fragility() – five-level fragility classification, auto-computes CFI.
• compute_cfi() / print_cfi() – CFI scoring and display.
• interpret_sensitivity() – concise template-based narrative interpretation.
• generate_report() – structured markdown/text report with CFI section.
• visualize_sensitivity() – sensitivity plot integration.
• sens_results S3 class for unified output across all functions.