feat(compliance): GET /sdk/v1/compliance/obligation-status (file-backed graph)

Vertical slice over the Compliance Execution Graph: obligation_id -> accepted
controls -> required evidence -> status. NEVER auto-asserts fulfillment - with
no evidence collection wired (MVP), a mapped obligation is "not_assessed" and
every required evidence is "missing". Fail-closed: no id -> 400; unknown id ->
unknown_obligation; mapped-but-no-control -> unmapped; graph not loaded -> 503.

- ComplianceGraphHandlers (separate from the DB-backed ObligationsHandlers):
  loads Registry join keys + accepted control mappings + evidence once at start.
- LoadComplianceGraph: candidate-path resolution across dev/container/test.
- Data plumbing: Dockerfile now COPYs data/{control_mappings,evidence_requirements,
  obligations}; data/obligations/obligation_join_keys.json is a SYNCED COPY of the
  repo-root Registry contract (re-sync on Registry growth).
- Table-driven handler test (mapped/unmapped/unknown/400 + no-fulfillment-claim).

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

ai-compliance-sdk/internal/app/routes.go

@@ -30,6 +30,7 @@ func registerRoutes(
 	maximizerHandlers *handlers.MaximizerHandlers,
 	regulatoryNewsHandlers *handlers.RegulatoryNewsHandlers,
 	useCaseHandler *handlers.UseCaseHandler,
+	complianceGraphHandlers *handlers.ComplianceGraphHandlers,
 ) {
 	v1 := router.Group("/sdk/v1")
 	{
@@ -54,6 +55,7 @@ func registerRoutes(
 		registerMaximizerRoutes(v1, maximizerHandlers)
 		registerUseCaseRoutes(v1, useCaseHandler)
 		v1.GET("/regulatory-news", regulatoryNewsHandlers.GetNews)
+		complianceGraphHandlers.RegisterRoutes(v1)
 	}
 }