Invalid case conversion of words containing digits

Strings such as `k8s` and `g2a` aren't correctly converted between UPPER_CASE and camelCase. Currently conversion algorithm treats boundaries between digits and letters as word boundaries. This leads to confusing conversions like:

```
k8sHost → K_8_S_HOST
K8S_HOST → k8SHost
```

Expected conversions:

```
k8sHost → K8S_HOST
K8S_HOST → k8sHost
```

The issue does not name files or tests; start by locating the case-conversion implementation in the TypeScript utilities. Add coverage for k8sHost and K8S_HOST, then verify the conversions preserve digit-containing words as shown in the expected examples.

Written by the indexing model from the issue text.