Add a changelog fragment

Added value: +"Part of the system that changed. Project-declared, so the accepted values vary; project_workspace reports them."

Added value: +"Markdown body, written below the frontmatter."

Added value: +"IDs of the cards this change came from."

Added value: +"IDs of decision records this change implements."

Added value: +"External issue or ticket references."

Added value: +"IDs of other records worth reading alongside."

Added value: +"Free-form tags for filtering."

Added value: +"The change, stated from the reader's side rather than the implementer's."

Added value: +"What kind of change this is — added, changed, fixed and so on. Project-declared, so the accepted values vary; project_workspace reports them."

Added value: +"Who the entry is rendered for, typically public or internal. Project-declared, so the accepted values vary; project_workspace reports them."

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "record": {
+      "additionalProperties": true,
+      "description": "A canonical record with its body, revision and reference graph.",
+      "properties": {
+        "archived": {
+          "description": "Whether the record lives in the archive directory.",
+          "type": "boolean"
+        },
+        "body": {
+          "description": "Markdown body below the frontmatter.",
+          "type": "string"
+        },
+        "created": {
+          "description": "Creation date, YYYY-MM-DD.",
+          "type": "string"
+        },
+        "file": {
+          "description": "File name within the collection directory.",
+          "type": "string"
+        },
+        "id": {
+          "description": "Stable record ID.",
+          "type": "string"
+        },
+        "incoming": {
+          "description": "Backlinks: references other records make to this one.",
+          "items": {
+            "additionalProperties": true,
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "incomingTotal": {
+          "description": "Total backlinks, which may exceed the returned page.",
+          "type": "integer"
+        },
+        "issues": {
+          "description": "Validation findings doctor would report for this record.",
+          "items": {
+            "additionalProperties": true,
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "kind": {
+          "description": "Record family: card, doc, change, release or memory.",
+          "type": "string"
+        },
+        "outgoing": {
+          "description": "References this record makes to others.",
+          "items": {
+            "additionalProperties": true,
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "path": {
+          "description": "Repository-relative path to the Markdown file.",
+          "type": "string"
+        },
+        "recordType": {
+          "description": "Type within the family.",
+          "type": "string"
+        },
+        "revision": {
+          "description": "Content hash to pass back as expectedRevision on the next write.",
+          "type": "string"
+        },
+        "status": {
+          "description": "Lifecycle status.",
+          "type": "string"
+        },
+        "tags": {
+          "description": "Free-form tags.",
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "title": {
+          "description": "Human-readable title.",
+          "type": "string"
+        },
+        "updated": {
+          "description": "Date of the last write, YYYY-MM-DD.",
+          "type": "string"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "required": [
+    "record"
+  ],
+  "type": "object"
+}