feat(joinir): Phase 191 body-local init integration into Pattern2

- Integrated LoopBodyLocalInitLowerer into Pattern2 lowering
- Fixed ValueId double-allocation issue (delegate to InitLowerer)
- Added body_ast parameter to lower_loop_with_break_minimal()
- Fixed json_program_loop.rs test for body-local scope
- New test: phase191_body_local_atoi.hako (expected: 123)

Supported init expressions:
- Integer literals, variable references, binary operations

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

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

apps/tests/phase191_body_local_atoi.hako

@@ -0,0 +1,33 @@
+// Phase 191: Body-local variable integration test
+// Tests: local digit = i + 1 (body-local) in number accumulation pattern
+//
+// This test verifies that LoopBodyLocalInitLowerer correctly lowers
+// body-local variable initialization expressions to JoinIR, and that
+// UpdateEnv resolves them during carrier update emission.
+//
+// Expected calculation:
+//   i=0: digit = 0+1 = 1, result = 0*10 + 1 = 1
+//   i=1: digit = 1+1 = 2, result = 1*10 + 2 = 12
+//   i=2: digit = 2+1 = 3, result = 12*10 + 3 = 123
+//   i=3: break (condition i >= 3)
+// Expected result: 123
+
+static box Main {
+    main() {
+        local result
+        result = 0
+        local i
+        i = 0
+        loop(i < 10) {
+            if i >= 3 {
+                break
+            }
+            // Phase 191: Body-local variable with initialization expression
+            local digit = i + 1
+            result = result * 10 + digit
+            i = i + 1
+        }
+        print(result)
+        return 0
+    }
+}