chore(mcp): add Smithery stdio config for crw-mcp

[us]

Adds a repo-root smithery.yaml so crw-mcp can be listed and installed via Smithery (smithery.ai).

What

• smithery.yaml with a startCommand.type: stdio block that launches the published crw-mcp npm package: npx -y crw-mcp.
• configSchema exposes one optional field crwApiKey, mapped to the CRW_API_KEY env var the binary already reads. Optional because the free tier and self-host work without a key.
• exampleConfig uses a placeholder key (no secret committed).

Why

Smithery has two publish paths: the URL method (a hosted streamable-HTTP + OAuth endpoint, already served at https://fastcrw.com/mcp) and the local stdio path. This file enables the local stdio install; the remote endpoint is listed separately via Smithery`s URL method and needs no repo file.

Notes

• File must live at repo root for Smithery to find it; matches the stdio schema used across published Smithery servers.
• No Rust/config touched, so the pre-commit Rust suite is a no-op for this change.
• Publishing the listing itself is a one-time manual step on smithery.ai (GitHub-OAuth connect / URL submit); this PR only lands the config.