[BUG] `/plugin marketplace update` does not pull latest Git commits from remote

Description

The /plugin marketplace update <marketplace-name> command does not synchronize with the latest Git commits from the remote repository. The marketplace stays on the commit it was initially installed with, even when new commits have been pushed to the main branch on GitHub.

Steps to Reproduce

1. Install a marketplace: /plugin marketplace add github:owner/repo
2. Author pushes new commits to the marketplace repository on GitHub (e.g., updating plugin version from 1.1.1 to 1.1.2)
3. Run /plugin marketplace update marketplace-name
4. Check the local marketplace directory: cd ~/.claude/plugins/marketplaces/marketplace-name && git log

Expected Behavior

The update command should:

• Perform a git fetch origin to retrieve the latest commits from the remote
• Perform a git pull origin <main-branch> to synchronize with the main branch (master/main)
• Update the local marketplace files to reflect the latest version

Actual Behavior

• The marketplace stays on the initial commit from installation
• No git synchronization occurs with the remote repository
• The lastUpdated timestamp in ~/.claude/plugins/known_marketplaces.json gets updated, but the actual git repository is not synchronized
• Plugin versions remain outdated even though new versions exist on GitHub

Workaround

Manual git pull is required:

cd ~/.claude/plugins/marketplaces/marketplace-name
git fetch origin
git pull origin master

After this manual operation, the plugin version is correctly updated.

Environment

• Claude Code version: 2.0.25
• OS: macOS 26.0.1 (Sequoia)
• Shell: zsh

Additional Context

The same issue occurs even after:

• Running /plugin marketplace remove and /plugin marketplace add (reinstalling the marketplace)
• The marketplace is installed via HTTPS (not SSH)

The git repository shows it's correctly configured (git remote -v shows the correct GitHub URL), but git fetch + git pull must be done manually to synchronize.