fix(skill): trim generated module reference output

[samzong]

Summary

• Trim generated module reference markdown to end with a single newline instead of a trailing blank line.
• Document skill.bundle installation in the README and CLI usage guide.
• Add a proposed workflow command design document.

Verification

• rtk go test ./internal/codegen/render
• tmpbin="$(mktemp -t lathe-local.XXXXXX)" && rtk go build -o "$tmpbin" ./cmd/lathe && (cd /Users/x/git/samzong/awire/cli && "$tmpbin" bootstrap -manifest cmd/awirectl/cli.yaml -overlay internal/overlay && gofmt -w internal/generated && git diff --exit-code -- internal/generated/ skills/awirectl/)

Compatibility

Generated CLI command shape, catalog schema, auth, body, and output behavior are unchanged. Generated Skill module reference markdown now avoids an extra trailing blank line. docs/workflow.md is marked proposed and does not add runtime behavior.

Checklist

• Tests or focused verification cover the changed surface.
• User-facing behavior changes are documented.
• Generated output under internal/generated/, .cache/, and ad-hoc skills/<cli-name>/ directories is not committed.
• Commits are signed off when this is ready to merge.