ENV Cleanup Step 4: Gate HAKMEM_WATCH_ADDR in tiny_region_id.h

Gate get_watch_addr() debug functionality with HAKMEM_BUILD_RELEASE,
returning 0 in release builds to disable address watching overhead.

Performance: 30.31M ops/s (baseline: 30.2M)

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

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

core/tiny_region_id.h

@@ -56,6 +56,7 @@ static inline uint32_t watcher_self_u32(void) {
 // Address watcher: Tracks when a specific address is allocated or freed
 // Usage: HAKMEM_WATCH_ADDR=0x7f1234567890 ./program
 static inline uintptr_t get_watch_addr(void) {
+#if !HAKMEM_BUILD_RELEASE
     static uintptr_t watch_addr = 0;
     static int initialized = 0;
 
@@ -77,6 +78,9 @@ static inline uintptr_t get_watch_addr(void) {
     }
 
     return watch_addr;
+#else
+    return 0;
+#endif
 }
 
 // Allocation source tracking