feat(phase-5.5): Begin final verification and cleanup

- Phase 5-5 started with lib build successful (only deprecated warnings)
- Discovered issue: RefNew still being generated in MIR output
- Need to investigate where RefNew is still being produced

Progress: MIR 35→26 reduction 95% complete

local_tests/test_mir_26_simple.nyash

@@ -0,0 +1,11 @@
+// Test simple program with MIR 26 instruction set
+static box Main {
+    main() {
+        local console = new ConsoleBox()
+        local message = "Hello from MIR 26!"
+        console.log(message)
+        
+        local result = 42
+        return result
+    }
+}