plugin update doesn't re-download files when version changes

Description

claude plugin update reports success and updates the version in metadata, but doesn't re-download plugin files when the version changes. This means new commands, skills, or changes in the plugin are never loaded.

Steps to Reproduce

1. Install a plugin from a marketplace: claude plugin install myplugin@mymarketplace --scope project
2. Push a new version of the plugin to the marketplace (e.g., add a new command file)
3. Run claude plugin marketplace update mymarketplace
4. Run claude plugin update myplugin@mymarketplace --scope project
5. Restart Claude Code

Expected: New command is available
Actual: New command is NOT available. Version number in claude plugin list shows the new version, but the files are stale.

Investigation

Checking the cache directory reveals the issue:

# Before update - only old version cached
ls ~/.claude/plugins/cache/mymarketplace/myplugin/
# 0.3.13

# After marketplace update + plugin update
ls ~/.claude/plugins/cache/mymarketplace/myplugin/
# Still only 0.3.13 - new version (0.3.14) was never downloaded

The marketplace clone IS updated (git pull happens), and installed_plugins.json IS updated with the new version number, but the actual plugin files are not re-downloaded.

Workaround

Delete the cache directory before installing:

rm -rf ~/.claude/plugins/cache/mymarketplace/
claude plugin install myplugin@mymarketplace --scope project

This forces a fresh download but is inefficient.

Environment

• Claude Code version: 2.1.12
• OS: macOS / Linux (WSL)
• Tested with marketplace-based plugins (GitHub URL marketplaces)

Suggestion

Either:

1. Fix plugin update to re-download files when version changes
2. Add a --force flag to force re-download
3. Document that plugin update only updates metadata (if this is intentional)