ci: split rust checks into focused jobs

[ubugeeei]

Summary

• Split the single rust CI job into focused metadata, format, check, clippy, and test jobs.
• Keep bench manual-only through workflow_dispatch.
• Add explicit rustfmt/clippy toolchain components where those jobs need them.
• Mirror the split in package scripts with check:wasm and test:doc, and update ci:local to run the same layers locally.

Local validation before push

• pnpm ci:local
• YAML parse for workflow/dependabot files
• git diff --check

Closes #26