docs: align consolidated solver workflow

phases/linear-static-3d-euler-beam/step21.md

@@ -11,10 +11,10 @@
 - `/AGENTS.md`
 - `/docs/ARCHITECTURE.md`
 - `/docs/ADR.md`
-- `/docs/requirements/linear-static-3d-euler-beam.md`
-- `/docs/formulations/3d-isoparametric-euler-beam-formulation.md`
-- `/docs/io-definitions/linear-static-3d-euler-beam-io.md`
-- `/docs/implementation-plans/linear-static-3d-euler-beam.md`
+- `/docs/linear-static-3d-euler-beam/requirements.md`
+- `/docs/linear-static-3d-euler-beam/formulation.md`
+- `/docs/linear-static-3d-euler-beam/io.md`
+- `/docs/linear-static-3d-euler-beam/implementation-plan.md`
 - `/include/fesa/analysis/analysis_model.hpp`
 - `/include/fesa/fem/dof_manager.hpp`
 - `/include/fesa/constraints/essential_constraints.hpp`
@@ -81,7 +81,7 @@ ctest --test-dir .harness/build -C Debug --output-on-failure
 1. nodal load/effective RHS tests를 먼저 작성하고 RED를 확인한다.
 2. nodal-only deterministic assembly와 RHS 최소 구현으로 GREEN을 만든다.
 3. nonzero prescribed displacement와 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 21 section에 실제 RED/GREEN/VERIFY command, exit code,
    핵심 output과 변경 파일을 기록한다.
 5. Step 21을 `completed`로 갱신하고 load/RHS evidence를 summary에 기록한다.