Document and demonstrate native and layered configuration loading

resource_context.go

@@ -4,7 +4,8 @@ import "io/fs"
 
 // ResourceContext provides a passive rooted filesystem view and a
 // slash-relative BaseDir for one acquired source. FS is borrowed: caller-owned
-// filesystems remain under caller control, and host files are opened afresh.
+// filesystems remain under caller control, while a host context opens a fresh
+// contained root for each resource open rather than retaining a loading handle.
 // Querying this record performs no I/O. Resource contents may change after
 // loading; callers must close files they open through FS.
 type ResourceContext struct {