fix: deduplicate range callbacks and align public declarations

[thedhanawada]

Summary

• Deliver exactly one initial range callback with both legacy and current interface readiness behavior, while preserving later navigation callbacks and React StrictMode cleanup.
• Remove conflicting global element declarations and use NodeNext-compatible declaration imports.
• Test against published core 2.5.5 and interface 1.8.0, retain existing peer compatibility floors, and add CI for the regression suite.
• Apply the compatible development-only undici security update.

Verification

• Clean npm ci, build, strict Bundler and NodeNext consumer type checks.
• 27 runtime/SSR tests, including actual interface integration and legacy 1.6 behavior.
• npm audit: zero vulnerabilities.
• Cross-package packed React/Vue/core/interface consumer verification passed.

Release

Compatible bugfix; publish patch 0.3.1 through the existing manual Publish to npm workflow after green CI and merge. No credential changes.