SVARtca 1.0.0

• Initial release (renamed from TCA to SVARtca to avoid CRAN name conflict).
• Implements Transmission Channel Analysis (Wegner, Lieb, Smeekes 2025).
• Three decomposition modes: overlapping, exhaustive 3-way, exhaustive 4-way.
• Systems form construction from VAR coefficient matrices.
• Integration with the vars package via tca_from_var().
• Plotting with plot_tca() (ggplot2).
• Binary additivity validation with tca_validate_additivity().