Prepare v0.4.0 prerelease and release skill

[brianhdk]

Summary

• advance the repository release version from 0.3.0 to 0.4.0
• regenerate synchronized marketplace manifests and all five native executables at the new embedded version
• prepare the first prerelease containing both Relewise and Relewise Developer
• add the internal release-relewise-agent-plugins maintainer skill for repeatable two-phase releases with required Trello tracking

After merge, creating the matching v0.4.0 tag will validate and publish the prerelease with five Gemini Relewise archives plus the Relewise and Relewise Developer Claude plugin ZIPs.

Trello: https://trello.com/c/gplntHyH/21543-agent-plugins-create-baseline

Verification

• Refresh marketplace payload completed successfully
• all pull-request validation checks passed on the generated payload
• the internal skill passes both repository and Agent Skills specification validation