feat: add CITATION.cff and .zenodo.json for academic citation support (#2291)

* feat: add CITATION.cff and .zenodo.json for academic citation support

Adds a Citation File Format file (CITATION.cff) so GitHub surfaces a
native "Cite this repository" button, and a .zenodo.json metadata file
so Zenodo can pre-fill the DOI record once a maintainer enables the
integration at zenodo.org.

Closes #2269

* fix: address PR review feedback on citation metadata

- Fix 'a specify CLI' -> 'the Specify CLI' in both files
- Broaden description to include extensions, presets, and workflows
- Remove empty orcid fields from .zenodo.json creators
- Update date-released to 2026-04-17 (actual 0.7.3 release date)

* fix: correct docs URL in CITATION.cff to github.io domain

.zenodo.json

@@ -0,0 +1,29 @@
+{
+  "title": "Spec Kit",
+  "description": "Spec Kit is an open source toolkit for Spec-Driven Development (SDD) — a methodology that helps software teams build high-quality software faster by focusing on product scenarios and predictable outcomes. It provides the Specify CLI, slash-command templates, extensions, presets, workflows, and integrations for popular AI coding agents.",
+  "creators": [
+    {
+      "name": "Delimarsky, Den"
+    },
+    {
+      "name": "Riem, Manfred"
+    }
+  ],
+  "license": "MIT",
+  "upload_type": "software",
+  "keywords": [
+    "spec-driven development",
+    "ai coding agents",
+    "software engineering",
+    "cli",
+    "copilot",
+    "specification"
+  ],
+  "related_identifiers": [
+    {
+      "identifier": "https://github.com/github/spec-kit",
+      "relation": "isSupplementTo",
+      "scheme": "url"
+    }
+  ]
+}

CITATION.cff

@@ -0,0 +1,31 @@
+cff-version: 1.2.0
+message: >-
+  If you use Spec Kit in your research or reference it in a paper,
+  please cite it using the metadata below.
+type: software
+title: "Spec Kit"
+abstract: >-
+  Spec Kit is an open source toolkit for Spec-Driven Development (SDD) —
+  a methodology that helps software teams build high-quality software faster
+  by focusing on product scenarios and predictable outcomes. It provides the
+  Specify CLI, slash-command templates, extensions, presets, workflows, and
+  integrations for popular AI coding agents.
+authors:
+  - given-names: Den
+    family-names: Delimarsky
+    alias: localden
+  - given-names: Manfred
+    family-names: Riem
+    alias: mnriem
+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"
+keywords:
+  - spec-driven development
+  - ai coding agents
+  - software engineering
+  - cli
+  - copilot
+  - specification