feat(skills): add document-review skill for brainstorm/plan refinement

[tmchow]

Summary

Adds the document-review skill for improving brainstorm and plan documents through structured review, plus renames /plan_review → /technical_review for clarity.

Changes

New document-review skill

A 6-step structured review process for improving document quality:

1. Get the document - Read provided path or find recent brainstorm/plan
2. Assess - Surface issues via reflective questions (What is unclear? What is unnecessary? What decision is being avoided?)
3. Evaluate - Score against criteria (clarity, completeness, specificity, YAGNI)
4. Identify critical improvement - Highlight the most impactful issue
5. Make changes - Auto-fix minor issues, ask approval for substantive changes
6. Offer next action - "Refine again" or "Review complete"

Key design decisions:

• Generic and reusable (not coupled to specific workflows)
• Soft iteration guidance (recommends 2 passes, doesn't enforce)
• Returns control to calling workflow for next-step decisions

Renamed /plan_review → /technical_review

The old name was confusing because "plan review" sounds like document review. The command actually spawns code-focused agents (DHH, Kieran, Simplicity) that review technical approach and architecture, not document quality.

• document-review = document quality (clarity, YAGNI, structure)
• /technical_review = technical approach (Rails conventions, code patterns, architecture)

Updated /workflows:brainstorm

Phase 4 handoff now offers "Review and refine" option. After document-review completes, brainstorm.md presents workflow-specific next steps:

1. Move to planning - Continue to /workflows:plan with this document
2. Done for now - Brainstorming complete. To start planning later: /workflows:plan [document-path]

Why "Done for now"? After brainstorming and multiple refinement iterations, the context window can be full of back-and-forth that's no longer needed. "Done for now" lets users start a fresh session for planning with a clean context window, using only the finalized brainstorm document as input.

Updated /workflows:plan

Post-generation options now include:

4. Review and refine - Load document-review skill for document quality pass

This complements /technical_review (option 3) which reviews the technical approach.

Updated README.md

• Added document-review skill to skills table
• Renamed /plan_review → /technical_review in commands table

How it works

brainstorm/plan completes
    ↓
"Review and refine?" → loads document-review skill
    ↓
skill reviews document, makes changes with approval
    ↓
"Refine again" or "Review complete"
    ↓
calling workflow presents next steps

Test plan

• Run /workflows:brainstorm and select "Review and refine" at handoff
• Verify document-review skill loads and applies review questions
• Verify changes require approval before substantive edits
• After review completes, verify brainstorm.md presents next step options
• Run /workflows:plan and select "Review and refine"
• Run /technical_review and verify it still works with new name
• Test standalone invocation: load document-review skill directly on a document