chore: release 0.3.0

[OndrejDrapalik]

Summary

Cuts 0.3.0 from #23 and #25. A feat in a pre-1.0 project bumps the minor, the rule this repo's
own history sets. Both version files move together, since CI's version-check and the release
workflow each assert independently that they match the tag.

One bullet, two merges — deliberately

Only #25 gets a changelog entry. This changelog documents plugin behaviour a user can observe, and
nothing in it has ever mentioned contributor tooling — #23 adds an agent skill under
.agents/skills/, which changes nothing about how the plugin behaves. Giving it a bullet would be
the first entry of its kind and would pad release notes people read to find out what changed for
them.

[Unreleased] is left in place and empty, so the next contributor's bullet has a home instead of
landing inside a published section — the trap that needed cleaning up in 0.2.0.

Verification before tagging

• scripts/changelog-notes.sh 0.3.0 extracts a non-empty section — an empty one hard-fails the
  release workflow after it has built three binaries, with the tag already public
• Both version files read 0.3.0; v0.3.0 is free; full suite green

Test plan

• npm test and the Rust suite green on main before cutting
• v0.3.0 publishes with all three dashboard binaries attached