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-num_str-carrier-design.md

@@ -1,8 +1,9 @@
 # Phase 245B: num_str Carrier Design Document
 
-**Status**: Design Phase
+**Status**: Implemented (Phase 245B-IMPL)
 **Target**: `_parse_number` loop の `num_str` 文字列キャリア対応
 **Scope**: Pattern 2 (loop with break) + 既存インフラ活用
+**Notes**: jsonparser_parse_number_real フィクスチャを Structured→Normalized→MIR(direct) で実装し、`num_str = num_str + ch` を LoopState キャリアとして dev テスト固定済み。
 
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