Release v1.6.4

[YASoftwareDev]

Release v1.6.4 — see CHANGELOG.md

Summary

• Add ~/.config/nvim/local.lua override support: sourced at end of init.lua via dofile if the file is readable
• Add example templates for all four machine-local override files: zsh, tmux, nvim, git
• Update README Machine-specific config section into a table with all overrides and template paths
• Update CLAUDE.md symlink table with the three new example files

Test plan

• CI matrix passes (9 install + 6 nosudo combinations)
• nvim local.lua sourcing is behaviour-only for machines that have the file; no change for machines without it