docrot-scan-api v1.4.1 — absolute root docs pointer + edge replay root check

v1.4.1 — Root docs pointer absolute (discovery-chain fix)

Problem: GET / returned "docs": "docs/API.md" — relative, resolving against the service base and 404ing behind the edge, while .well-known/agent-service.json carried the correct absolute URL. Machine consumers following the root's docs field hit a dead link.

Fix: root docs now equals the descriptor's absolute GitHub URL. The edge contract replay gained a root-discovery check (17 → 18): docs must be an absolute https:// URL. Regression assertion in test_root_describes_service; suite 119 green.

Found by: tracing the public discovery chain (story → repo → root → docs) instead of trusting that each link works.