docs: align consolidated solver workflow

phases/linear-static-3d-euler-beam/step20.md

@@ -11,8 +11,8 @@
 - `/AGENTS.md`
 - `/docs/ARCHITECTURE.md`
 - `/docs/ADR.md`
-- `/docs/requirements/linear-static-3d-euler-beam.md`
-- `/docs/implementation-plans/linear-static-3d-euler-beam.md`
+- `/docs/linear-static-3d-euler-beam/requirements.md`
+- `/docs/linear-static-3d-euler-beam/implementation-plan.md`
 - `/include/fesa/core/status.hpp`
 - `/include/fesa/core/diagnostic.hpp`
 - `/include/fesa/math/vector.hpp`
@@ -97,7 +97,7 @@ if ($LASTEXITCODE -ne 1) { throw 'Public-header dependency scan failed' }
 1. adapter tests를 먼저 작성하고 missing solver RED를 확인한다.
 2. factorize/solve phase를 분리한 최소 PARDISO adapter로 GREEN을 만든다.
 3. repeated RHS, RAII, residual, public boundary와 전체 VERIFY를 확인한다.
-4. `/docs/implementation-plans/linear-static-3d-euler-beam-implementation-report.md`의
+4. `/docs/linear-static-3d-euler-beam/implementation-report.md`의
    Step 20 section에 실제 RED/GREEN/VERIFY command, exit code,
    핵심 output과 변경 파일을 기록한다.
 5. Step 20을 `completed`로 갱신하고 factorization/substitution evidence를 summary에 기록한다.