refactor(reasoning): enforce ClaimCoverage (Welt 1) vs ComplianceStatus (Welt 2) boundary [F1]

Architecture-validation finding: the implementation mode produced compliance-
flavored output ("teilweise erfüllt", "covered") from a mere customer claim,
blurring the line to the Execution layer. This is a design decision, not a text
fix — the reasoning layer judges only the customer's STATEMENT, never conformity.

- CoverageStatus -> ClaimCoverage; values are claim-relative + carry "potential":
  potentially_addresses / partially_addresses / does_not_address /
  insufficient_information.
- ImplementationAssessment -> ClaimObligationMapping (coverage_status ->
  claim_coverage); ImplementationResponse -> ImplementationReasoningResponse
  (assessments -> mappings, + explicit `disclaimer`); request renamed; engine
  entry assess_implementation -> reason_implementation_claim.
- Endpoint /reasoning/implementation-assessment -> /reasoning/implementation-reasoning.
- Summary/explanations reworded: "adressiert wahrscheinlich N Pflichten … für
  eine Bewertung der tatsächlichen Umsetzung sind Nachweise erforderlich (keine
  Konformitätsaussage)". No "erfüllt"/"abgedeckt" leaks.
- New guard test asserts no compliance verdict leaks (no "erfüllt"; disclaimer
  separates ClaimCoverage from ComplianceStatus). 23 tests green, mypy clean.

Discovery (scope/obligations) was already structurally claim-free and unaffected.

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

backend-compliance/compliance/api/reasoning_routes.py

@@ -5,7 +5,7 @@ pure deterministic rule evaluation.
 
     POST /reasoning/scope                      -> which regulations apply + missing facts
     POST /reasoning/obligations                -> obligations, overlaps, multi-evidence
-    POST /reasoning/implementation-assessment  -> claim coverage per obligation
+    POST /reasoning/implementation-reasoning   -> claim->obligation mapping (Welt 1, no verdict)
     POST /reasoning/interpretation-assessment  -> verdict on a customer interpretation
 """
 
@@ -14,14 +14,14 @@ from __future__ import annotations
 from fastapi import APIRouter
 
 from compliance.reasoning import (
-    assess_implementation,
     assess_interpretation,
     derive_obligations,
     discover_scope,
+    reason_implementation_claim,
 )
 from compliance.reasoning.schemas import (
-    ImplementationRequest,
-    ImplementationResponse,
+    ImplementationReasoningRequest,
+    ImplementationReasoningResponse,
     InterpretationRequest,
     InterpretationResponse,
     ObligationsRequest,
@@ -48,9 +48,9 @@ def applicable_obligations(req: ObligationsRequest) -> ObligationsResponse:
     return derive_obligations(req.product_profile, req.regulatory_scope)
 
 
-@router.post("/implementation-assessment", response_model=ImplementationResponse)
-def implementation_assessment(req: ImplementationRequest) -> ImplementationResponse:
-    return assess_implementation(req.product_profile, req.customer_claim)
+@router.post("/implementation-reasoning", response_model=ImplementationReasoningResponse)
+def implementation_reasoning(req: ImplementationReasoningRequest) -> ImplementationReasoningResponse:
+    return reason_implementation_claim(req.product_profile, req.customer_claim)
 
 
 @router.post("/interpretation-assessment", response_model=InterpretationResponse)