docs: document year and year_month display_type host contract

assets/examples/year-month-action.example.json

@@ -0,0 +1,40 @@
+{
+  "_comment": "形状参考：账期/月份字段用 year_month，宿主渲染年月选择器。完整契约见 references/ACTIONS.md「表单字段类型对照」与 references/SCHEMA.md。",
+  "schemaVersion": 1,
+  "skill": "your-skill-slug",
+  "actions": [
+    {
+      "id": "create-period-job",
+      "label": "新建账期作业（示例）",
+      "description": "演示 year_month 字段：提交值为 YYYY-MM 字符串，不要用 date。",
+      "placements": ["toolbar"],
+      "executionProfile": "sync",
+      "interaction": "form",
+      "bind": {
+        "tables": ["close_jobs"]
+      },
+      "entrypoint": {
+        "type": "cli",
+        "command": "create-job",
+        "args": ["--period", "{{period}}", "--title", "{{title}}"]
+      },
+      "inputSchema": {
+        "type": "object",
+        "required": ["period"],
+        "properties": {
+          "period": {
+            "type": "string",
+            "title": "月份",
+            "description": "格式 YYYY-MM，例如 2026-05",
+            "display_type": "year_month"
+          },
+          "title": {
+            "type": "string",
+            "title": "标题",
+            "description": "可留空，默认按月份生成"
+          }
+        }
+      }
+    }
+  ]
+}