fix: keep fast-element exports explicit

[janechu]

Pull Request

📖 Description

• keep optional binding and hydration export paths separate instead of collapsing them into binding.js / hydration.js
• remove wildcard barrel re-exports from fast-element secondary entrypoints by making index.debug.ts, index.rollup.ts, and index.rollup.debug.ts explicit
• remove the temporary package-exports regression test and the grouped binding/exports.ts / hydration/exports.ts source files
• keep metadata.js and pending-task.js out of the public export map
• update docs, examples, skills, and generated export-size docs to reflect the dedicated subpaths

🎫 Issues

• Fixes Update exports to be more granular #7245

👩‍💻 Reviewer Notes

• declarative.ts continues to own the hydratable-template side effect via the existing side-effect import
• install-element-hydration.js and install-hydratable-view-templates.js stay as dedicated side-effect entrypoints
• npm run checkchange reports that no new change files are needed

📑 Test Plan

• npm run build
• npm run prebuild -w sites/website
• npm run biome:check
• npm run checkchange
• npx playwright test src/components/hydration.pw.spec.ts src/components/element-controller.pw.spec.ts --project=chromium

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

[janechu]

Abandoning this, context was lost due to a misunderstanding of barrel exports.