`calculateCost`, `modelsAreEqual`, and `getBundledProviders` moved from the
`@oh-my-pi/pi-ai` barrel to `@oh-my-pi/pi-catalog/models` in the catalog
split (1b9d9d0851). The legacy-extension pi-ai root shim already bridged
`getBundledModel`/`getBundledModels` back under their old `getModel`/
`getModels` names but never re-exported the other relocated symbols, so any
legacy extension importing `calculateCost` from `@oh-my-pi/pi-ai` failed
plugin validation at install time with `Export named 'calculateCost' not
found in module '.../legacy-pi-ai-shim.ts'`.
Bridge all three symbols through the shim so pre-split legacy extensions
load again. Add regression tests that load fixtures importing
`calculateCost`, `modelsAreEqual`, and `getBundledProviders` from
`@oh-my-pi/pi-ai` and assert identity against the catalog implementations.
Fixes#4584
roboomp
5203fce696