Add e2e test for CLI plugin loading

[Copilot]

Adds an e2e scenario for CLI plugin loading in a new test/extra/ directory, separating secondary functionality tests from core framework tests.

Test coverage

• Plugin list: Verifies magek plugins command works via @oclif/plugin-plugins
• Plugin install: Installs @magek/adapter-event-store-nedb from local Verdaccio registry
• Plugin visibility: Asserts the installed plugin appears in subsequent magek plugins output

Structure

New file: packages/e2e-tests/test/extra/cli-plugins.e2e.test.ts

Follows the same sequential steps-based dependency pattern and reuses all existing harness modules (exec, app, verdaccio, rush, etc.). No changes needed to .mocharc.yml or tsconfig.test.json — existing recursive: true and test/**/* globs pick up the new path automatically.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Implement an e2e test for cli plugins</issue_title>
<issue_description>Implement an e2e scenario where we load a cli plugin in the end-to-end tests. In our existing e2e tests, we used the terminology "Phase 1, 2..." because these are core functionalities of our framework, but plugin loading is secondary (important also, but not key). Let's create a folder called "extra" and a script dedicated to CLI plugins there called "cli_plugin.sh" or similar (choose a descriptive name)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Implement an e2e test for cli plugins #654

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