Size estimate low, based on constructor.yaml options

### Checklist

- [x] I added a descriptive title
- [x] I searched open reports and couldn't find a duplicate

### What happened?

Creating a new installer estimates the total size of the install lower than the actual size on disk.

### Additional Context

The install estimate is off because of selected `construct.yaml` options.

```yaml
keep_pkgs: true
condarc:
allow_softlinks: false
always_copy: true
```

This set of options ends up with more disk space needed because `always_copy: true` creates a copy.

Reproduce the installer size estimate using the selected constructor.yaml options: keep_pkgs: true, condarc.allow_softlinks: false, and condarc.always_copy: true. Trace where the estimate is calculated and compare it with the resulting on-disk size; done means the estimate accounts for the extra space required when always_copy is true.

Written by the indexing model from the issue text.