Don't require rust-analyzer

[esafak]

Not every user is working on Rust. The server shouldn't fail because rust-analyzer is not installed. At least show how to disable the Rust MCP in the README. Thanks.

[bug-ops]

Thanks for the report — confirmed. The server currently fails if rust-analyzer isn’t installed, which shouldn’t block non‑Rust users. Actively fixing this in PR #34 by adding graceful LSP server degradation so one failed server doesn’t stop the whole system. I’ll update this issue as the remaining phases in PR #34 land.