[BUG] User-scope plugin MCP server cannot access project directory — no cwd or env var pointing to project root

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Description

When a plugin is installed with --scope user, its MCP server process has no way to know the current project directory. The server's process.cwd() points to the plugin cache path (~/.claude/plugins/cache/...), not the project root.

This means any MCP server that needs a project-level config file (e.g. .db-fetcher.json in project root) will fail on startup or at tool invocation time.

Steps to Reproduce

1. Create a plugin with an MCP server that reads a config file from process.cwd()
2. Install the plugin: claude plugin install my-plugin@my-marketplace --scope user
3. Place the config file in the project root (e.g. C:\Projects\my-app\.my-config.json)
4. Open Claude Code in that project
5. The MCP server fails — process.cwd() is the plugin cache directory, not the project root

Expected Behavior

The MCP server should be able to discover the current project root, either via:

• process.cwd() set to the project root (like project-scope plugins)
• An environment variable like CLAUDE_PROJECT_DIR

Actual Behavior

• process.cwd() = ~/.claude/plugins/cache/{marketplace}/{plugin}/{version}/
• No environment variable provides the project path
• Only CLAUDE_PLUGIN_ROOT and CLAUDE_PLUGIN_DATA are available

Workaround

Install with --scope project instead. This works because projectPath in installed_plugins.json tells Claude Code where to set the cwd.

Environment

• Claude Code: VS Code Extension
• OS: Windows 11
• Plugin system version: latest

Related Issues

• #33815 — CLAUDE_PROJECT_DIR is empty/unset
• #26429 — Feature request to expose project root

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