phsl / new-api

* fix: prevent model create from wiping existing pricing for same name

* fix(models): keep create from wiping pricing for any existing name

Prefilling from the drawer's open-time model name only covered the
missing-models entry point. Submit deletes the pricing entries for the
name in the form, which is editable and starts empty from the toolbar
"Create model" button, so both a hand-typed existing name and a renamed
prefill still dropped the configured pricing.

Track the name whose pricing was actually read into the form and scope
the delete-then-readd to it, or to a name the user explicitly priced.
Editing still clears pricing by emptying the fields, a prefilled create
does too, and a name the form never loaded is left alone -- which also
stops an edit that renames onto an existing name from destroying that
name's pricing.

Read the prefill through one shared readPricingConfig instead of
duplicating the seven-map parse in both branches, and open the advanced
section for ratios that are configured as 0 rather than only truthy ones.