[Bug]: aspect cli is downloaded twice

### What happened?

We observe that bootstrapping via `bazelisk` is downloading `aspect-cli` twice.

```
$ bazel
2026/01/14 09:18:51 Downloading https://github.com/aspect-build/aspect-cli-legacy/releases/download/2025.51.5/bazel-2025.51.5-linux-x86_64...
2026/01/14 09:18:51 Skipping basic authentication for github.com because no credentials found in /home/timotheus/.netrc
Downloading: 52 MB out of 52 MB (100%)
2026/01/14 09:19:45 Downloading https://github.com/aspect-build/aspect-cli-legacy/releases/download/2025.51.5/bazel-2025.51.5-linux-x86_64...
2026/01/14 09:19:45 Skipping basic authentication for github.com because no credentials found in /home/timotheus/.netrc
Downloading: 52 MB out of 52 MB (100%)
2026/01/14 09:20:37 Downloading https://releases.bazel.build/8.5.0/release/bazel-8.5.0-linux-x86_64...
2026/01/14 09:20:37 Skipping basic authentication for releases.bazel.build because no credentials found in /home/timotheus/.netrc
Downloading: 61 MB out of 61 MB (100%)
Aspect CLI is a better frontend for running bazel

Usage:
aspect [command]
...
```

### Version

```
$ bazel --version
aspect 2025.51.5-80ea9104
```

### How to reproduce

```shell
Reproduction:
* Download https://github.com/bazelbuild/bazelisk/releases/download/v1.27.0/bazelisk-amd64.deb
* Clean up bazelisk cache: `rm -rf ~/.cache/bazelisk`
* Create minimal project:

$ touch WORKSPACE
$ cat .bazeliskrc
BAZELISK_BASE_URL=https://github.com/aspect-build/aspect-cli-legacy/releases/download
USE_BAZEL_VERSION=aspect/2025.51.5
$ cat .bazelversion
8.5.0
$ bazel
# see trace from above -> aspect cli is downloaded twice
```

### Any other information?

I created the issue here and not on `bazelisk` as I don't see that issue when using plain `bazel` aka no `aspect-cli`.

Start with the .bazeliskrc and .bazelversion settings in the reproduction, then trace the bazelisk bootstrap and cache behavior for the BAZELISK_BASE_URL and USE_BAZEL_VERSION values. Run the provided minimal-project reproduction after clearing ~/.cache/bazelisk; done means aspect-cli is downloaded only once before the expected Bazel download and startup.

Written by the indexing model from the issue text.