[imitater-dou]

Motivation

A few instructions in DEVELOPMENT.md no longer match the repository layout on main, so following them fails:

1. Getting started says cd core && cargo test, but there is no top-level core/ directory anymore (the core crates were moved under crates/core/). The --features debug example further down (syscall::precompiles::edwards::ed_add::tests::test_ed_add_simple) belongs to sp1-core-machine in crates/core/machine, which is also where the debug feature is defined.
2. Contributing to Docs says to run mdbook serve in the top-level directory, but the book was removed in chore(docs): remove book #2105 (docs migrated elsewhere), and there is no book.toml anywhere in the tree.
3. Publishing links to .github/workflows/release-plz.yml, which was removed in fix: Remove release-plz workflow, and fix some issues in release.yml #2576.

Repro on main (9e94952):

gh api repos/succinctlabs/sp1/contents/core?ref=main                              # 404
gh api repos/succinctlabs/sp1/contents/book.toml?ref=main                         # 404
gh api repos/succinctlabs/sp1/contents/.github/workflows/release-plz.yml?ref=main # 404
gh api repos/succinctlabs/sp1/contents/crates/core/machine?ref=main               # 200

Solution

• cd core -> cd crates/core/machine.
• Replace the mdbook commands with a pointer to the published docs at https://docs.succinct.xyz/docs/sp1/introduction.
• Drop the dead release-plz.yml link and keep the release-plz.toml reference, which still exists. I left the rest of the Publishing section unchanged since the release flow is maintainer-owned.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes