Transient timeout fetching manifests have increased significantly
recently, especially with private runners.
```
Fetching manifest data from https://raw.githubusercontent.com/astral-sh/versions/main/v1/uv.ndjson ...
Error: The operation was aborted due to timeout
```
Retry transient manifest network failures up to three times with a
progressive backoff (not exponential), keeping the total wait bounded
while making setup resilient to short network blips.
Co-authored-by: Raymond <arguile-@users.noreply.github.com>
