feat: PROVING GROUND — dogfood validation milestone

[flyingrobots]

Overview

PROVING GROUND (Milestone 5 of 7) validates that git-mind can answer 5 real project management questions about a realistic project graph.

Deliverables

• PRV-SEED: Echo ecosystem YAML seed (~55 nodes, ~70 edges)
• PRV-VIEW: New coverage view (code-to-spec gap analysis)
• PRV-TEST: Integration test: import seed + answer 5 questions + timing
• PRV-DOCS: Dogfood session transcript

The 5 Questions

1. What blocks M2? → milestone view
2. Which ADRs lack implementation? → traceability view
3. Which crates are unlinked to specs? → NEW coverage view
4. What should a new engineer read first? → onboarding view
5. What's low-confidence? → suggestions view + computeStatus()

Depends On

• BEDROCK (feat: git-mind v2 — rewrite on @git-stunts/git-warp #180) ✅
• WATCHTOWER (feat: git mind status dashboard command (WATCHTOWER) #185) ✅
• INTAKE (feat: YAML import pipeline (git mind import) — INTAKE milestone #187) ✅
• PRISM (feat: declarative view engine + 4 new views (PRISM milestone) #189) ✅