chore: Release 3.9.0

[github-actions]

Channels: Current

🚀 New Features

• feat: notification show feedback (feat: notification show feedback #417)

🐛 Bug Fixes

• fix: [SDK-4340] skip enqueueing metabox assets for disallowed post types (fix: [SDK-4340] skip enqueueing metabox assets for disallowed post types #418)

🏗️ Other Updates

• chore: bump Tested up to WordPress Core version

[claude]

Straightforward release PR: version bump and changelog update.

Extended reasoning...

Overview

This PR bumps the plugin version from 3.8.1 to 3.9.0 in two places: the plugin header and ONESIGNAL_PLUGIN_VERSION constant in onesignal.php, and the Stable tag plus changelog entry in readme.txt. No code logic is modified.

Security risks

None. The changes are limited to version strings and human-readable changelog text. The ONESIGNAL_PLUGIN_VERSION constant only flows into the SDK wrapper header value, which is benign.

Level of scrutiny

Minimal — this is a mechanical release prep PR. Versions are internally consistent (3.9.0 ↔ 030900) across both files, and the changelog entries align with the merged PRs visible in recent git history (#415–#422 plus #417/#418).

Other factors

No bugs were flagged by the bug hunting system, no prior reviews to reconcile, and the PR is small and self-contained.