Add sop-onboard skill and agent for project onboarding

[ldraney]

Summary

• New /sop-onboard skill: step-by-step playbook for setting up dev-sop-engine in any project
• New sop-onboard agent: autonomous onboarding assistant that follows the playbook
• Tested on ~/ebay-sdk (see Set up dev-sop-engine for project configuration ebay-sdk#12)

Test plan

• .claude/skills/sop-onboard/SKILL.md generated with correct content
• .claude/agents/sop-onboard.md generated with YAML frontmatter
• ~/ebay-sdk/.claude/ generated from its own sop/sop.json
• PR open on ebay-sdk: Set up dev-sop-engine for project configuration ebay-sdk#12

Closes #35

🤖 Generated with Claude Code

[ldraney]

Review Notes

Good

• Thorough step-by-step playbook, well-structured flow (analyze → issue → branch → scaffold → generate → verify → PR)
• Agent prompt has a solid decision framework for when to add rules/MCP/skills/agents
• "Start minimal" philosophy is sound
• Tested on a real project (ebay-sdk PR #12)

Issues / Suggestions

1. Whitespace-only reformatting in sop.json — The diff expands single-line arrays to multi-line throughout. This noise makes actual changes harder to review. Consider separating formatting from functional changes.

2. .current-issue changed from 6 to 35 — Should this file be in .gitignore? Looks like transient state.

3. Script copying underspecified (Step 6) — Says "Copy from dev-sop-engine's reference implementation" but doesn't say how. A new user wouldn't know where to get engine.sh, no-main-commit.sh, or log-event.sh. This is the weakest part of the playbook.

4. No mention of CLAUDE.md — The playbook doesn't address setting up a project's CLAUDE.md, which is a key part of Claude Code configuration.

5. Skill is 197 lines — Not a blocker, but the agent consumes all of it each time it's invoked.

🤖 Generated with Claude Code