feat(joinir): Phase 89 P0 - Continue + Early Return pattern detector

## Pattern4 Detector 締め
- is_pattern4_continue_minimal() を厳しく
- Select 必須 + conditional Jump exactly 1
- loop 内 return を P4 と誤認しない

## 新パターン箱
- LoopPattern::ContinueReturn enum 追加
- has_return_in_loop_body() helper 追加
- Fail-Fast: UnimplementedPattern error

## Normalized-dev 統合
- NormalizedDevShape::PatternContinueReturnMinimal
- detector: Select + conditional Jumps >= 2
- canonical には入れない（dev-only）

## Documentation
- 10-Now.md, CURRENT_TASK.md 更新

Impact:
- 987 lib tests PASS
- 60 normalized_dev tests PASS
- Pattern4 誤爆防止

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

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

src/mir/join_ir_vm_bridge/bridge.rs

@@ -140,6 +140,10 @@ fn normalize_for_shape(
                 .expect("P4 object normalization failed")
             },
         )),
+        // Phase 89: Continue + Early Return pattern (dev-only, delegates to P2 for now)
+        NormalizedDevShape::PatternContinueReturnMinimal => {
+            catch_unwind(AssertUnwindSafe(|| normalize_pattern2_minimal(module)))
+        }
     };
 
     match result {