chore(release): v0.4.0

[lbb00]

What does this PR do?

Release v0.4.0: bump @devicekit/devices and @devicekit/frame from 0.3.0 to 0.4.0 (minor — Unreleased only added the screenCorners feature and the Duo-outer fix that depends on it, nothing breaking), and turn the accumulated ## [Unreleased] section of CHANGELOG.md into ## [0.4.0] - 2026-09-14, per CONTRIBUTING.md's release steps.

How was this verified?

• pnpm build, pnpm test, pnpm lint, pnpm check-types, pnpm run verify:pack — all exit 0 (same one pre-existing react(refs) warning noted in chore(lint): drop ESLint in favor of oxlint #25, non-blocking).
• verify:pack confirms the packed tarballs are devicekit-frame-0.4.0.tgz / matching devices version and every export still resolves from the tarball.

Checklist

• Tests added or updated — n/a, release-only change
• pnpm lint passes with zero warnings — one pre-existing-pattern warning remains (see chore(lint): drop ESLint in favor of oxlint #25), not new
• CHANGELOG.md updated under ## [Unreleased] — moved into ## [0.4.0]

🤖 Generated with Claude Code