chore: cleanup proposals, plans, and reports folder structure

- Move completed proposes (HINTS-STRUCTURED-LABEL) to propose/completed/
- Move stale proposes to propose/stale/ (ENHANCED-ROLE-RECOGNITION, INDEX-AUTO-MODE, TIER2-INCREMENTAL-REBUILD, RANKING-MICROSERVICE)
- Move completed plans to plans/completed/ (PLAN-DESCRIBE-HINTS-STRUCTURAL, AGENT-PROMPTS-DESCRIBE-HINTS-STRUCTURAL)
- Create propose/active/ and plans/active/ for future active items
- Move PRODUCT-VISION.md to docs/
- Move CODEBASE_REQUIREMENTS.md to docs/
- Remove reports/ folder (call-graph-review.md, what-to-borrow-from-cmm.md, review/)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: HumanBean17