APT repo for unstable references missing .deb files

Looking at the Packages file for the [latest snapshot toolchain on Debian](https://apt.llvm.org/unstable/dists/llvm-toolchain/main/binary-amd64/Packages) you find references to .deb files like `python3-clang-23_23~++20260211113928+77513e7d740b-1~exp1~20260211114101.3385_amd64.deb` that cannot be found in the repo:

```console
$ curl -s -I 'https://apt.llvm.org/unstable/pool/main/l/llvm-toolchain-snapshot/python3-clang-23_23~++20260211113928+77513e7d740b-1~exp1~20260211114101.3385_amd64.deb'
HTTP/2 404
server: nginx/1.18.0 (Ubuntu)
content-type: text/html
via: 1.1 varnish, 1.1 varnish
accept-ranges: bytes
age: 0
date: Fri, 20 Feb 2026 22:49:51 GMT
x-served-by: cache-bur-kbur8200103-BUR, cache-fra-etou8220088-FRA
x-cache: MISS, MISS
x-cache-hits: 0, 0
x-timer: S1771627791.300440,VS0,VE313
strict-transport-security: max-age=300
content-length: 162
```

The same version for Ubuntu 24.04 (noble) is available.