docs: Phase 123 DONE
Updates documentation to reflect Phase 123 completion.
**Updates**:
1. `docs/development/current/main/phases/phase-123/README.md`:
- Marked all success criteria as complete
- Added comprehensive DONE section with implementation details
- Documented key design decisions (graceful degradation, fail-fast, box-first)
- Added verification commands and next steps (Phase 124)
2. `docs/development/current/main/10-Now.md`:
- Moved Phase 123 from "Next" to "2025-12-18: Phase 123 完了"
- Added Phase 123 summary (Return literal, If minimal compare, graceful degradation)
- Updated "Next" to Phase 124 (Normalized reads facts + Return(Variable))
3. `docs/development/current/main/01-JoinIR-Selfhost-INDEX.md`:
- Added Phase 123 entry: "Normalized semantics (Return literal + If minimal compare, dev-only)"
**Phase 123 Summary**:
- P0: Docs complete, scope frozen ✅
- P1: Return(Integer literal) working ✅
- P2: Return(Variable) returns Ok(None) (graceful degradation) ✅
- P3: If(minimal compare) generates correct JoinIR ✅
- P4: Integration smoke passing ✅
- P5: Docs updated ✅
**Verification**:
- Unit tests: 8 passed
- Integration smoke: PASS
- Legacy tests: Still passing (graceful degradation confirmed)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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