feat(joinir): Phase 248 - Normalized JoinIR infrastructure

Major refactoring of JoinIR normalization pipeline:

Key changes:
- Structured→Normalized→MIR(direct) pipeline established
- ShapeGuard enhanced with Pattern2 loop validation
- dev_env.rs: New development fixtures and env control
- fixtures.rs: jsonparser_parse_number_real fixture
- normalized_bridge/direct.rs: Direct MIR generation from Normalized
- pattern2_step_schedule.rs: Extracted step scheduling logic

Files changed:
- normalized.rs: Enhanced NormalizedJoinModule with DevEnv support
- shape_guard.rs: Pattern2-specific validation (+300 lines)
- normalized_bridge.rs: Unified bridge with direct path
- loop_with_break_minimal.rs: Integrated step scheduling
- Deleted: step_schedule.rs (moved to pattern2_step_schedule.rs)

New files:
- param_guess.rs: Loop parameter inference
- pattern2_step_schedule.rs: Step scheduling for Pattern2
- phase43-norm-canon-p2-mid.md: Design doc

Tests: 937/937 PASS (+6 from baseline 931)

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

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

docs/development/current/main/phase245b-jsonparser-num-str-carrier-design.md

@@ -1,5 +1,6 @@
-Status: Draft  
-Scope: `_parse_number` で `num_str` を Pattern2/P5 のキャリアとして扱うかどうかを決める設計フェーズ（コード変更なし）。
+Status: Implemented (Phase 245B-IMPL)  
+Scope: `_parse_number` で `num_str` を Pattern2/P5 のキャリアとして扱うかどうかを決める設計フェーズ（実装は Structured→Normalized dev フィクスチャで完了）。
+Notes: jsonparser_parse_number_real フィクスチャで `num_str = num_str + ch` を LoopState キャリアとして実装し、dev Normalized 比較テストで固定済み。
 
 # Phase 245B: JsonParser `_parse_number` の `num_str` キャリア設計