Preserve runtime-targeted anchors

[chubes4]

Summary

• preserve behavior-bearing anchors as exact bounded runtime DOM before logo/button/native-link dispatch rewrites them
• retain selector identity for source scripts and runtime dependency parity
• add artifact-level coverage for one runtime anchor island without duplicate diagnostics

Evidence

• composer test:canonical passes on current trunk
• University eight-surface run e46ab296-3f5c-4794-b6e8-979ceecdcfca improved Events from 14.00% / -106px to 8.92% / -9px; the other seven routes remained at their validated baseline
• Runtime dependency parity resolves .event-add against preserved markup

AI assistance

• Model: OpenAI GPT-5.6 Sol
• Tool: OpenCode
• Use: source investigation, implementation, regression coverage, canonical testing, and rendered evidence analysis

Chris Huber reviewed and remains responsible for the change.