docs: remove retired workflow instructions and repair references

phases/linear-static-3d-euler-beam/step4.md

@@ -1,20 +1,16 @@
 # Step 4: I/O Contract
 
-## 담당 역할과 필수 스킬
-
-- 담당 역할: `io-definition-agent`
-- 필수 스킬: `fesa-io-contract`
-- 스킬을 끝까지 읽고 semantic contract만 정의하라. C++ API는 다음 gate가 담당한다.
+> 과거 개발 계획이다. 아래 작업·상태·예시는 현재 실행 지시가 아니다.
+> 현재 구현과 검증 한계는 [기능 요약](../../docs/linear-static-3d-euler-beam/README.md)을 따른다.
 
 ## 읽어야 할 파일
 
 - `/AGENTS.md`
-- `/docs/SOLVER_AGENT_DESIGN.md`
-- `/.codex/skills/fesa-io-contract/SKILL.md`
-- `/docs/linear-static-3d-euler-beam/requirements.md`
-- `/docs/linear-static-3d-euler-beam/formulation.md`
-- `/docs/linear-static-3d-euler-beam/numerical-review.md`
-- `/docs/superpowers/specs/2026-08-08-linear-static-3d-euler-beam-design.md`
+- `../../docs/solver-core/README.md`
+- `../../docs/linear-static-3d-euler-beam/README.md`
+- `../../docs/linear-static-3d-euler-beam/formulation.md`
+- `../../docs/linear-static-3d-euler-beam/README.md`
+- `../../docs/solver-core/README.md`
 - `/reference/cantilever beam/cantilever beam.inp`
 - `/reference/cantilever beam/cantilever beam displacements.csv`
 - `/reference/cantilever beam/cantilever beam reactions.csv`
@@ -22,7 +18,7 @@
 
 ## 작업
 
-`docs/linear-static-3d-euler-beam/io.md`를 생성하라. Metadata status는
+`../../docs/linear-static-3d-euler-beam/README.md`를 생성하라. Metadata status는
 `ready-for-implementation-planning`으로 둔다.
 
 - 지원 keyword별 위치, parameter, data grammar, case policy, source-location 보존,