Fix TrackingAllocator reallocation_count being incremented on failed operations

The reallocation_count counter was being incremented regardless of whether
the resize/remap operations succeeded. This led to inaccurate memory
allocation statistics.

- resize: Only increment when rawResize returns true (success)
- remap: Only increment when rawRemap returns non-null (success)

This fixes the TODO comments that were present in the code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/test_runner.zig

@@ -501,7 +501,7 @@ pub const TrackingAllocator = struct {
         defer self.mutex.unlock();
 
         const result = self.parent_allocator.rawResize(old_mem, alignment, new_len, ra);
-        self.reallocation_count += 1; // TODO: only if result is not null?
+        if (result) self.reallocation_count += 1;
         return result;
     }
 
@@ -531,7 +531,7 @@ pub const TrackingAllocator = struct {
         defer self.mutex.unlock();
 
         const result = self.parent_allocator.rawRemap(memory, alignment, new_len, ret_addr);
-        self.reallocation_count += 1; // TODO: only if result is not null?
+        if (result != null) self.reallocation_count += 1;
         return result;
     }
 };