Initial dotfiles: portable shell configs, Brewfile, and setup guide

Cleaned up for new machine portability: removed hardcoded paths,
EOL packages, and redundant version managers. Consolidated NVM
loading, added work git identity support via includeIf.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fzf.zsh

@@ -0,0 +1,7 @@
+# Setup fzf
+# ---------
+if [[ ! "$PATH" == */opt/homebrew/opt/fzf/bin* ]]; then
+  PATH="${PATH:+${PATH}:}/opt/homebrew/opt/fzf/bin"
+fi
+
+source <(fzf --zsh)