docs: zero to hero tutorial — build your first LEZ program with SPEL

[jimmy-claw]

Summary

SPEL has no user-facing documentation. New developers have no entry point.

Create a docs/tutorial.md that walks through building a complete LEZ program from scratch using SPEL.

Outline

1. Prerequisites — Rust, risc0 toolchain, sequencer running locally
2. Scaffold — create a new program crate, add lez-framework dependency
3. Write your first instruction — #[lez_program], #[instruction], account validation
4. State accounts — define a PDA, derive it, store/read state
5. Build and deploy — make build, lez-cli deploy
6. Call it — lez-cli run or via generated FFI
7. Register in SPELbook — registry register --idl-path ...
8. Next steps — ChainedCall, multisig governance, client-gen

Notes

• Use a simple counter program as the example (increment, get_count)
• Reference logos-co/lez-multisig as a real-world example
• Tracks with issue docs: zero to hero tutorial — build your first LEZ program with SPEL #61 (full reference docs)