refactor(skills): 技能库 - 将内置 Markdown 包移至 backend/builtin

backend/builtin/embed.go

@@ -0,0 +1,11 @@
+package builtin
+
+import "embed"
+
+// FS contains the built-in skill packages shipped with the backend.
+//
+// The Markdown packages live outside internal Go packages so they are easy to
+// review and maintain as product content while remaining embedded in binaries.
+//
+//go:embed *
+var FS embed.FS