clang-format: hangs when a CASE macro is defined and used

The following simple `.clang-format` file, defining a `CASE` macro, results in a hang when trying to format the following simple `poc.cc` file.
```
$ cat .clang-format
Macros:
- CASE=case

$ cat poc.cc
int f() {
switch (42) {
#define CASE(kind)
CASE(1)
CASE(2)
#undef CASE
}
}

$ ./clang-format -version
clang-format version 21.1.3 (https://github.com/llvm/llvm-project 450f52eec88f728c89a9efd667dbeaf2dad93826)

$ ./clang-format poc.cc
^Cinterrupted
```

Reproduce the hang with the .clang-format configuration and poc.cc example using ./clang-format poc.cc. Start by tracing clang-format's handling of the CASE macro around the switch statement; done means the command completes without hanging while preserving the expected formatting.

Written by the indexing model from the issue text.