feat: add checks list command using versioned API

[thebiglabasky]

Summary

• Adds checkly checks list CLI command using the new versioned /api/checks endpoint
• Adds REST client with auto-pagination support and X-Checkly-API-Version header
• Supports filtering by check type, tag, muted, and activated status

Companion PR

• monorepo: https://github.com/checkly/monorepo/pull/424 (backend versioned API surface)

Note

This is an exploration/discussion PR — not intended for merge as-is.

Test plan

• Run npx checkly checks list against a test account
• Verify filtering flags work (--check-type, --tag, --activated, --muted)
• Verify --json output format

🤖 Generated with Claude Code

[MichaelHogers]

@thebiglabasky hey hey, i would personally go for:

• publish contract from backend upon merge into main, public npm package for our CLI (because our CLI is a public repo)
• import this contract into CLI, so we don't hardcode any types/paths/wahtever here, all should just be a single source of truth coming from backend

we should nail this tomorrow, Javier did this alrdy but next step is to move to https://trpc.io/ and allow to create domain specific sdks (@kiroushi)

[thebiglabasky]

Absolutely. For now I went with a quick n' dirty path to try out the API versioning path but don't expect this to be mergeable. I had the exact same thought about having shared types across repos to ensure consistency. That's tied to versioning too so good to get right