Add work-specific configs and enhance git/shell setup

- Add modular zsh configs: zshrc-dev for dev tools, zshrc-natera for work
- Add .gitignore to exclude private Natera config from version control
- Configure git commit signing and delta diff viewer in gitconfig
- Regenerate p10k.zsh with rainbow theme and improved visual settings
- Add HIST_IGNORE_SPACE option to prevent saving sensitive commands
- Document Natera machine setup with private config template in README

zshrc

@@ -36,6 +36,7 @@ setopt HIST_FIND_NO_DUPS      # Don't display duplicates when searching
 setopt HIST_REDUCE_BLANKS     # Remove unnecessary blanks
 setopt INC_APPEND_HISTORY     # Add commands to history immediately
 setopt EXTENDED_HISTORY       # Record command start time and duration
+setopt HIST_IGNORE_SPACE      # Don't save commands starting with space (for sensitive commands)
 
 # Directory Navigation
 setopt AUTO_CD                # Change directories without typing cd
@@ -154,7 +155,6 @@ alias h='history'
 alias path='echo -e ${PATH//:/\\n}'  # Pretty print PATH
 alias now='date +"%T"'
 alias nowdate='date +"%d-%m-%Y"'
-
 [ -f ~/.fzf.zsh ] && source ~/.fzf.zsh
 
 # Docker CLI completions
@@ -163,3 +163,9 @@ if [[ -d "$HOME/.docker/completions" ]]; then
 fi
 autoload -Uz compinit
 compinit
+
+# Developer enhancements
+[[ -f ~/dotfiles/zshrc-dev ]] && source ~/dotfiles/zshrc-dev
+
+# Natera-specific config (loaded last; only on Natera machines when this file exists)
+[[ -f ~/dotfiles/zshrc-natera ]] && source ~/dotfiles/zshrc-natera