Add ConfigKit version 5 document boundary

internal/core/config/load.go

@@ -0,0 +1,60 @@
+package config
+
+import (
+	configkit "gitea.maximumdirect.net/eric/ConfigKit"
+)
+
+// LoadOptions contains configuration selections supplied by an application
+// boundary. It is intentionally narrow: configuration discovery and CLI flag
+// parsing remain outside this package.
+type LoadOptions struct {
+	Profile   string
+	Overrides []configkit.Override
+}
+
+// loadDocument is the private ConfigKit load boundary under construction.
+// Production commands continue to use the existing version 4 loader until the
+// runtime conversion and command wiring are complete.
+func loadDocument(path string, options LoadOptions) (*configkit.Result[Document], error) {
+	return loadDocumentSource(configkit.File(path), options)
+}
+
+func loadDocumentSource(source configkit.Source, options LoadOptions) (*configkit.Result[Document], error) {
+	return configkit.Load(source, configkit.Options[Document]{
+		Definition: documentDefinition(),
+		Profile:    options.Profile,
+		Overrides:  options.Overrides,
+	})
+}
+
+func documentDefinition() configkit.Definition[Document] {
+	return configkit.Definition[Document]{
+		Defaults: func() Document {
+			return Document{
+				Pipelines: map[string]PipelineDocument{},
+				Concurrency: &ConcurrencyDocument{
+					StageWorkers: map[string]int{},
+				},
+			}
+		},
+		Version: &configkit.VersionRule{
+			Path:  configkit.Keys("version"),
+			Check: validateDocumentVersion,
+		},
+	}
+}
+
+func validateDocumentVersion(version configkit.Version, validation *configkit.Validation) error {
+	if !version.Present || version.Null {
+		validation.Error(configkit.Keys("version"), "configuration version is required")
+		return nil
+	}
+	if version.Text == "4" {
+		validation.Error(configkit.Keys("version"), "configuration version 4 is no longer supported; migrate to version 5")
+		return nil
+	}
+	if version.Text != "5" {
+		validation.Error(configkit.Keys("version"), "unsupported configuration version")
+	}
+	return nil
+}