Run Preact unit tests on build outputs for npm

### Description

Bento Preact/React functional components have a `test-component.js` unit test file that we run against the corresponding `component.js` file. On npm, we release files that are built from `component.js`, but not tested against `test-component.js`. We should consider doing so to prevent unnecessary broken npm binaries like the one reported in #35741.

### Alternatives Considered

n/a

### Additional Context

_No response_

Start by locating the Bento Preact/React component.js and matching test-component.js files, then trace how the npm release build produces its outputs. Run the existing component unit tests against the built files and verify that every released output is covered, including the failure scenario from issue #35741.

Written by the indexing model from the issue text.