docs(changelog): promote the Unreleased entries under 0.2.0

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Summary

copier update targets the latest SemVer tag rather than HEAD, so the core.hooksPath fix and in_existing_repo support merged in PR #13 reach no downstream project until a tag exists. This cuts the release commit so v0.2.0 can be tagged.

Changes

• Promotes the [Unreleased] entries under ## [0.2.0] - 2026-09-02 and adds the compare-link references, per the Release section of AGENTS.md.
• Minor, not patch. Of the three downstream-visible commits since v0.1.1, one is feat(template) (the in_existing_repo answer: additive, false by default, so existing downstreams keep their layout) and two are fix(template).
• No template or code changes ride along; the diff is CHANGELOG.md only.

Testing

• Docs-only change; no automated tests apply. The changelog was cross-checked against git log v0.1.1..main -- template/ copier.yml: 3 commits, all covered by the 3 promoted entries. The fourth commit in the range (fix(tests), the hook-install test rendering from HEAD) is maintainer-only and deliberately absent.

Notes for reviewers

• Merging does not release anything. The tag is a separate step and must be applied to the merge commit on main:
  git tag -a v0.2.0 -m "v0.2.0" && git push origin v0.2.0, then git describe --tags to confirm a reachable tag exists.
• Until that tag is pushed, downstreams stay on v0.1.1; the nested project in the dogfood repo cannot copier update to pick up in_existing_repo before then.

Related

• Follows PR feat(template): add in_existing_repo for scaffolding into an existing repo #13, which landed every entry promoted here.