feat: add jiangchang platform kit skeleton

Add a shared SDK scaffold for entitlement checks and a reusable Gitea release workflow template to standardize skill packaging and publishing across projects.

sdk/pyproject.toml

@@ -0,0 +1,19 @@
+[build-system]
+requires = ["setuptools>=68", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "jiangchang-skill-core"
+version = "0.1.0"
+description = "Common entitlement SDK for Jiangchang skills"
+requires-python = ">=3.10"
+dependencies = [
+  "requests>=2.31.0",
+]
+
+[tool.setuptools]
+package-dir = {"" = "."}
+
+[tool.setuptools.packages.find]
+where = ["."]
+include = ["jiangchang_skill_core*"]