list command doesn't mark default runtime

I have 3.13 and 3.14-dev installed, and `py list` doesn't show the default (should be 3.14).

Verbose output includes:
```
# Filtering installs by tag = 3.14
# Filter did not include pythoncore-3.13-64
# Filter did not include pythoncore-3.14-64
# tag '3.14' matched 0 installs
# default_platform '-64' matched 0 installs
# Reusing unfiltered list
```