fix(www): fix fileName lookup in rehype-component's ComponentSource

[zigzagdev]

Description

The ComponentSource file lookup in rehype-component.ts only matched files entries that were plain strings, but every entry declared in registry-ui.ts / registry-examples.ts is an object ({ path, type, target }), so the fileName attribute was effectively ignored and the lookup always fell back to files[0].
Added a helper that reads the path from either shape and used it in the lookup.

Changes

• Add a getFilePath() helper that reads the path from a files entry regardless of whether it's a plain string or an object ({ path, type, target })
• Use it in ComponentSource's fileName search so it correctly matches against the object form (the shape actually used throughout the registry)

Motivation

The files.find() predicate only checked typeof file === "string", which is always false since every registry item declares its files as objects.
As a result, the fileName attribute on <ComponentSource name="..." fileName="..."> was silently ignored and the code always fell back to the first file.

Breaking Changes

None.

Screenshots

Device / Browser / Viewport:

Before	After

N/A

Checklist

• pnpm check passes locally
• pnpm build passes locally
• pnpm build:registry was run and the generated files are committed (if you changed registry/ or config/site.ts — CI verifies this on every PR)
• PR title follows Conventional Commits (e.g., feat(marquee): add reverse prop)

[vercel]

@zigzagdev is attempting to deploy a commit to the product-studio Team on Vercel.

A member of the Team first needs to authorize it.