feat(llvm): Phase 97 Box/Policy refactoring complete

Box化完了:
- CallRoutePolicyBox: Call routing SSoT
- PrintArgMarshallerBox: Print marshalling SSoT
- TypeFactsBox: Type propagation SSoT
- PhiSnapshotPolicyBox: PHI contract SSoT
- PluginErrorContext: Structured error reporting

📋 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/development/current/main/01-JoinIR-Selfhost-INDEX.md

@@ -53,6 +53,8 @@ JoinIR の箱構造と責務、ループ/if の lowering パターンを把握
    - `docs/development/current/main/phases/phase-96/README.md`
 10. Phase 97: MiniJsonLoader LLVM EXE parity（next_non_ws / escape）
     - `docs/development/current/main/phases/phase-97/README.md`
+11. Phase 98: Plugin loader fail-fast + LLVM parity持続化
+    - `docs/development/current/main/phases/phase-98/README.md`
 6. MIR Builder（Context 分割の入口）
    - `src/mir/builder/README.md`
 7. Scope/BindingId（shadowing・束縛同一性の段階移行）