fix(release): run marketplace kit with Bun

[smackgg]

Summary

• execute the pinned Marketplace Kit CLI with the same Bun runtime as the official build wrapper instead of following its Node shebang
• cover the exact resolved CLI invocation in tooling tests
• advance Nexus to recovery version 0.3.10 because 0.3.9 reached main but its protected Release failed before any tag or asset was published

Root cause

@convax/marketplace-kit@0.1.0 uses Bun.file only when build-index --changed is present. The release wrapper previously launched the CLI through its Node shebang, so ordinary validation passed and the protected changed-version build failed with Bun is not defined.

Verification

• bun install --frozen-lockfile --ignore-scripts
• bun run check
• bun run pack
• bun run build:index
• real official build-index --changed invocation through the wrapper
• release plan selects only plugin/nexus-service@0.3.10