release: prepare 1.0.0-beta.4 - #43

What changed

• bump the root and public package versions to 1.0.0-beta.4
• archive the accumulated post-beta.3 work in a dated beta.4 Changelog section
• keep public installation on causescope@beta
• keep the standalone StackBlitz lab on published beta.3 until beta.4 exists on npm

Why

The current main includes user-visible keyboard accessibility, the versioned trace export contract and public types, plus expanded browser, API, external-beta, and release-readiness coverage. Publishing beta.4 makes that tested state available without prematurely advancing to RC or stable.

Impact

After this PR merges, the exact merge commit is eligible for the separately approved v1.0.0-beta.4 tag. This PR alone does not publish npm or create a GitHub Release.

Validation

• pnpm verify:release (11 policy tests)
• pnpm check
• pnpm test:e2e:firefox (3/3)
• packed-package Vite 5.4/6.4/7.3/8.1 consumers
• npm tarball dry-run: 21 allowlisted files, 119,653 bytes
• staged diff and privacy-pattern scan

Relates to #42