[John Kreitlow (radium-v)]

Pull Request

📖 Description

Reduce when overhead when both branches are fixed templates. The new path avoids creating and calling wrapper functions, and selects the result once when the condition is constant.

Template bindings still run only for the selected branch. A false condition without an else template still returns null. Includes regression tests and updated API docs and size reports.

👩‍💻 Reviewer Notes

Chromium microbenchmarks showed 25–29% lower construction time and 3–9% lower evaluation time for dynamic conditions with fixed templates. These measurements exclude DOM rendering.

The focused when export grows from 731 to 781 bytes gzipped.

📑 Test Plan

• All 13 tests in the focused when suite passed.
• Coverage includes constant and expression conditions, missing else templates, and fixed and bound template combinations.
• New tests check lazy evaluation, source and context forwarding, and subscription changes when the active branch changes.

✅ 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.

Agents

• I have linked to an existing issue in this project that this change addresses
• I have read the skills
• I have read the DESIGN.md file(s) in packages relevant to my changes
• I have updated the DESIGN.md file(s) in packages relevant to my changes