feat(explain): complete ATLAS-WP-0004 — graph edges, blast-radius, determinism tests
T05: tests/test_effective_config.py (6 tests) — order-independence, most-specific
winner, no value/secret leak; wired into make validate + CI.
T04: tools/blast_radius.py + make blast-radius — consumers, transitive dependents
(cycle-safe), secret refs, fan-out risk band.
T03: tools/config_graph.py + make graph/graph-query — emit config-typed edges to
registry/indexes/graph.yaml (queryable by surface id); staleness check in the gate.
WP-0004 finished (5/5). Read-first control-plane MVP complete: explain, graph,
and blast-radius over the seeded surfaces.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
tegwick
4620244f39