Fix status messages without TTY (#16785)
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## Summary
#12175 changed the behavior of `on_request_complete` when stderr is not
a tty to output `Downloading`/`Uploading` (via `Direction::as_str`).
This fixes it to output `Downloaded`/`Uploaded` again.
## Test Plan
Tested locally to verify new output.
Old:
```
$ uv sync --no-cache 2>&1 | tee /dev/null
Using CPython 3.14.0
Creating virtual environment at: .venv
Resolved 12 packages in 19ms
Downloading numpy (15.8MiB)
Downloading matplotlib (9.4MiB)
Downloading fonttools (4.6MiB)
Downloading pillow (6.7MiB)
Downloading kiwisolver (1.4MiB)
Downloading kiwisolver
Downloading fonttools
Downloading pillow
Downloading matplotlib
Downloading numpy
```
New:
```
$ uv sync --no-cache 2>&1 | tee /dev/null
Using CPython 3.14.0
Creating virtual environment at: .venv
Resolved 12 packages in 3ms
Downloading numpy (15.8MiB)
Downloading fonttools (4.6MiB)
Downloading matplotlib (9.4MiB)
Downloading kiwisolver (1.4MiB)
Downloading pillow (6.7MiB)
Downloaded kiwisolver
Downloaded pillow
Downloaded fonttools
Downloaded matplotlib
Downloaded numpy
```
