feat(joinir): Phase 224-B - MethodCallLowerer + CoreMethodId extension

- Extend CoreMethodId with is_pure(), allowed_in_condition(), allowed_in_init()
- New MethodCallLowerer box for metadata-driven MethodCall lowering
- Integrate MethodCall handling in condition_lowerer
- P0: Zero-argument methods (length) supported
- Design principle: NO method name hardcoding, CoreMethodId metadata only

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

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

apps/tests/phase224b_method_call_captured.hako

@@ -0,0 +1,25 @@
+// Phase 224-B: MethodCall lowering test - s.length() with captured variable
+//
+// Test case: Loop using s.length() where s is passed as parameter (captured)
+// This prevents constant folding and forces MethodCall lowering
+//
+// Pattern 2: Loop with captured variable
+
+static box Main {
+    helper(text) {
+        local i = 0
+
+        // Pattern 1 loop with MethodCall in condition (text is captured)
+        loop(i < text.length()) {
+            i = i + 1
+        }
+
+        return i
+    }
+
+    main() {
+        local result = me.helper("Hello")
+        print("result = " + result)
+        return result
+    }
+}

apps/tests/phase224b_method_call_min.hako

@@ -0,0 +1,22 @@
+// Phase 224-B: MethodCall lowering test - s.length() in loop condition
+//
+// Test case: Simple loop using s.length() in condition
+// Expected: MethodCall should be lowered to BoxCall instruction
+//
+// Pattern 1: Simple while loop (no break, no continue)
+
+static box Main {
+    main() {
+        local s = "Hello"
+        local i = 0
+
+        // Pattern 1 loop with MethodCall in condition
+        loop(i < s.length()) {
+            i = i + 1
+        }
+
+        // Output result
+        print("i = " + i)
+        return i
+    }
+}