SCEV verification fails with incorrect trip count after indvars

SCEV verification fails on a testcase with dead loop after indvars.
https://godbolt.org/z/989vcjvdq

To reproduce run:

```
opt -passes='loop(indvars),verify' test.ll
```

Error message:

```
Trip Count for Loop at depth 1 containing: %dead_loop
Changed!
Old: 1
New: 0
Delta: 1
...
#5 0x00007768c90287f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
#6 0x000000000487074c llvm::ScalarEvolution::verify() const (/opt/compiler-explorer/clang-21.1.0/bin/opt+0x487074c)
...
```

Start with the linked Godbolt testcase and reproduce the failure using opt with the loop(indvars) and verify passes. Read the ScalarEvolution verification path around the reported trip-count change for dead_loop; done means the testcase no longer reports an incorrect trip count or aborts verification.

Written by the indexing model from the issue text.