Fixes#363
The update command was hardcoded to use --global flag, which would
convert a local installation to a global one during updates.
Changes:
- Detect install type by checking ./.claude/ first, then ~/.claude/
- Use --local flag when updating a local install
- Use --global flag when updating a global install
- Update cache cleanup path to match install location
- Clarify warning message paths to be relative to install location
83845755b3