Add MCP tool registration tests

[quiloos39]

Summary

• Add tests verifying MCP tool registration for all four SSH tools (connect, execute, disconnect, list)
• Covers tool existence, metadata (titles, descriptions), input schema fields and counts, enabled state, duplicate registration prevention, and naming conventions

Test plan

• Run npx tsx tests/mcp-tools.test.ts and verify all tests pass
• Confirm tool names and schema fields match src/tools/*.ts registrations