Make all installation scripts idempotent

[slifty]

Problem

Many installation scripts cannot be safely re-run, causing errors or inconsistent state when running bootstrap.sh multiple times.

Specific Issues

1. zsh/install.sh reinstalls Oh My ZSH every time (will fail if already installed)
2. python/install.sh:2 tries to create plugins directory without checking if it exists
3. python/install.sh:3 creates symlink without checking if it already exists
4. homebrew/preinstall.sh:16 appends to .zprofile every time (creating duplicates)
5. macos/install.sh sets dock apps without checking current state

Impact

• Can't safely re-run bootstrap after initial setup
• Makes incremental updates/fixes difficult
• Causes confusing error messages
• May create duplicate configurations

Recommended Solution

Make all scripts idempotent by adding checks before operations:

# Example: Check before creating directory
if [ ! -d "$(pyenv root)/plugins" ]; then
  mkdir "$(pyenv root)/plugins"
fi

# Example: Check before creating symlink
if [ ! -L "$(pyenv root)/plugins/pyenv-install-latest" ]; then
  ln -s ~/.dotfiles/python/pyenv-install-latest "$(pyenv root)/plugins/pyenv-install-latest"
fi

# Example: Check if line already exists before appending
if ! grep -q "brew shellenv" "$HOME/.zprofile"; then
  echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> $HOME/.zprofile
fi

Success Criteria

• bootstrap.sh can be run multiple times without errors
• Scripts detect existing installations and skip redundant operations
• Clear messaging about what's being skipped vs. installed

Priority

MEDIUM - Important for maintainability and user experience

[slifty]

Completed ✓

All installation scripts have been updated to be idempotent. The bootstrap process can now be safely re-run multiple times without errors or duplicate configurations.

Fixed Scripts

Originally Identified Issues:

1. ✅ zsh/install.sh - Added check for Powerline Fonts before installation
2. ✅ python/install.sh - Added checks for Python version and pipenv before installation
3. ✅ homebrew/preinstall.sh - Added grep check before appending to .zprofile
4. ✅ macos/install.sh - Added checks for device name and launch agent
5. ✅ macos/preinstall.sh - Rosetta installation is already idempotent

Additionally Fixed:
6. ✅ direnv/install.sh - Added directory and symlink existence checks
7. ✅ system/install.sh - Added symlink check and process checks before opening apps
8. ✅ ots/install.sh - Added multiple checks for SVN config and password store

Pattern Applied

All scripts now follow the standard pattern from lib/functions.sh:

• Check if already configured before performing operations
• Display informative messages about skipped vs. new operations
• Exit gracefully when nothing needs to be done

Testing

All scripts can now be run multiple times safely. The bootstrap process will:

• Skip operations that are already complete
• Display clear messages about what's being done vs. skipped
• Continue through failures in individual scripts (tracked in bootstrap.sh)