[Test]: add MCP tool wrapper unit tests

[viiccwen]

Summary

Add deterministic unit tests for MCP permission checks and tool wrappers. Defer external dependency initialization until MCP server startup so importing the module remains side-effect free for unit tests.

Related Issue

Fixes #84

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Configuration or deployment
• Tests

Changes

• Cover allowed-channel, valid-member, non-member, and expired-member permission behavior.
• Cover check-in generation and member-service wrapper success/error responses with table-driven tests.
• Cover staff-only member notifications, custom and event delivery, missing events, and upcoming-event listings without live services.
• Move RAG, course catalog, and member database initialization from module import to the MCP entrypoint.

Testing

• Local tests or checks pass: make test (145 passed)
• Manual verification completed: make precommit and git diff --check
• Not tested; reason:

Impact Checklist

• Discord bot behavior checked, if affected
• MCP server behavior checked, if affected
• Webhook behavior checked, if affected
• Docker or compose changes checked, if affected
• Environment variables documented, if changed
• Logs do not expose secrets or sensitive data

Notes for Reviewers

The tests import MCP tool functions directly and mock member, course, and Discord boundaries. They do not start FastMCP/Uvicorn transports, initialize RAG models, fetch course data, or synchronize member data.