mi_usable_size: invalid (unaligned) pointer on MacOS Ventura.

Good day.

Have problems on MacOS Ventura with mimalloc: "(unaligned) pointer" warning in Debug and segfault in Release.
It seems that mi_usable_size gets pointer not allocated by mimalloc.

Sample code:

app.m

```
#include

@interface MyApplication : NSApplication
@end

@implementation MyApplication
@end

void
Cocoa_RegisterApp(void)
{
@autoreleasepool
{
if (NSApp == nil)
{
[MyApplication sharedApplication];
{
}
}
}
}

int main()
{
Cocoa_RegisterApp();
return 0;
}

```

CMakeLists.txt
```
cmake_minimum_required(VERSION 3.16)
project(test_package)
find_package(mimalloc)

add_executable(test_package app.m)
target_link_libraries(test_package PRIVATE mimalloc::mimalloc)

find_library(COCOA_LIBRARY Cocoa ONLY)
target_link_libraries(test_package PRIVATE ${COCOA_LIBRARY})
```

Debug output:
mimalloc: error: mi_usable_size: invalid (unaligned) pointer: 0x97f86e598e2153a3
mimalloc: error: mi_usable_size: invalid (unaligned) pointer: 0xa0cfe8d603a959b3
mimalloc: warning: mi_usable_size: pointer might not point to a valid heap region: 0x20d54b5b0
(this may still be a valid very large allocation (over 64MiB))
mimalloc: error: mi_usable_size: pointer does not point to a valid heap space: 0x20d54b5b0

Build the minimal reproduction from app.m with the CMakeLists.txt configuration and run it on macOS Ventura in Debug and Release. Start at the reported mi_usable_size calls and trace the pointer source; done means the sample no longer produces the invalid-pointer diagnostics or Release segfault.

Written by the indexing model from the issue text.