Implements the unraid_plugins MCP tool (3 actions, 1 destructive) and adds
elicit_destructive_confirmation() to core/setup to support all tools that
gate dangerous mutations behind confirm=True with optional MCP elicitation.
- _write_env now creates CREDENTIALS_DIR (mode 700) and writes credentials
to CREDENTIALS_ENV_PATH (mode 600) instead of PROJECT_ROOT/.env
- On first run (no .env yet), seeds file content from .env.example to
preserve comments and structure
- elicit_and_configure catches NotImplementedError from ctx.elicit() so
clients that don't support elicitation return False gracefully instead
of propagating the exception
- Updated test_elicit_and_configure_writes_env_file to patch CREDENTIALS_DIR
and CREDENTIALS_ENV_PATH instead of PROJECT_ROOT
- Added 5 new tests covering dir/file permissions, .env.example seeding,
in-place credential update, and NotImplementedError guard