Problem

When using claude-code-action on non-ephemeral self-hosted runners, the marketplace install step fails on the second run because the state from the previous run persists in ~/.claude/:

✘ Failed to add marketplace: Marketplace 'claude-code-plugins' is already installed.
Please remove it first using '/plugin marketplace remove claude-code-plugins' if you want to re-install it.

Expected behavior

The action should handle "already installed" gracefully — either skip the install if the marketplace is already present, or remove and re-install it.

Reproduction

1. Use a non-ephemeral self-hosted runner
2. Configure the action with plugin_marketplaces and plugins
3. First run succeeds
4. Second run on the same runner fails

Workaround

None that's safe for concurrent jobs. Deleting ~/.claude between runs risks breaking concurrent jobs on the same runner.

Environment

• Runner: self-hosted, non-ephemeral (GCP MIG)
• Action version: b113f49a56229d8276e2bf05743ad6900121239c
• Config: plugin_marketplaces: 'https://github.com/anthropics/claude-code.git'