Address review: use __addr_of for pointer semantics, add mcpi test

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Dnreikronos

test/src/ir_generation/tests/mcp_zero_len.sw

@@ -4,17 +4,23 @@ script;
 fn main() -> u64 {
     let src: u64 = 42;
     let mut dst: u64 = 0;
-    asm(dst_ptr: dst, src_ptr: src, zero: 0u64) {
+    asm(dst_ptr: __addr_of(dst), src_ptr: __addr_of(src), zero: 0u64) {
         mcp dst_ptr src_ptr zero;
     }
+    asm(dst_ptr: __addr_of(dst), src_ptr: __addr_of(src)) {
+        mcpi dst_ptr src_ptr i0;
+    }
     dst
 }
 
 // ::check-ir::
 
 // check: asm(dst_ptr: $VAL, src_ptr: $VAL, zero: $VAL) -> ()
 // check: mcp
+// check: asm(dst_ptr: $VAL, src_ptr: $VAL) -> ()
+// check: mcpi
 
 // ::check-asm::
 //
 // not: mcp
+// not: mcpi