release: prepare base-cli-demo 0.2.0 for publication #55

Prepare the next demo release after the merged Base-CLI 0.5.0 alignment in #47 and PR #48. Update VERSION, README release references, and CHANGELOG; run the authoritative validation and package checks; create the annotated v0.2.0 tag and GitHub draft release only after the preparation PR is merged; dispatch the draft asset workflow; then review checksums and compatibility evidence before separate publication authorization. This issue tracks preparation and evidence; it does not itself authorize publishing the immutable release.