chore: update CITATION.cff to v0.10.2 (2026-06-11) (#2966)

CITATION.cff was created at v0.7.3 (2026-04-17) and has not been
updated since. The latest stable release is v0.10.2, released on
2026-06-11. This brings the citation metadata in sync with the
published release so tools that ingest CITATION.cff (Zenodo, GitHub's
"Cite this repository" widget, citation managers) surface the correct
version.

Verification:
- `gh release list --repo github/spec-kit --limit 1` → v0.10.2 / 2026-06-11
- CHANGELOG.md `## [0.10.2] - 2026-06-11` confirms the date
- pyproject.toml `version = "0.10.3.dev0"` confirms 0.10.2 is latest stable

AI-assisted contribution.

CITATION.cff

@@ -20,8 +20,8 @@ authors:
 repository-code: "https://github.com/github/spec-kit"
 url: "https://github.github.io/spec-kit/"
 license: MIT
-version: "0.7.3"
-date-released: "2026-04-17"
+version: "0.10.2"
+date-released: "2026-06-11"
 keywords:
   - spec-driven development
   - ai coding agents