Implement artifact-level render command with Markdown output and update docs

internal/render/run.go

@@ -0,0 +1,72 @@
+package render
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"gitea.maximumdirect.net/eric/seriatim/internal/artifact"
+	"gitea.maximumdirect.net/eric/seriatim/internal/config"
+)
+
+// Run executes artifact-level render orchestration.
+func Run(ctx context.Context, cfg config.RenderConfig) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
+	data, err := os.ReadFile(cfg.InputFile)
+	if err != nil {
+		return fmt.Errorf("read --input-file %q: %w", cfg.InputFile, err)
+	}
+
+	inputArtifact, err := artifact.ParseOutputArtifactJSON(data)
+	if err != nil {
+		return fmt.Errorf("--input-file %q: %w", cfg.InputFile, err)
+	}
+
+	model, err := FromOutputArtifact(inputArtifact)
+	if err != nil {
+		return fmt.Errorf("normalize artifact for render: %w", err)
+	}
+
+	registry := NewRegistry()
+	renderer, err := registry.Resolve(cfg.Format)
+	if err != nil {
+		return err
+	}
+
+	rendered, err := renderer.Render(model, Options{
+		Title:             cfg.Title,
+		IncludeTimestamps: cfg.IncludeTimestamps,
+		IncludeSegmentIDs: cfg.IncludeSegmentIDs,
+		IncludeMetadata:   cfg.IncludeMetadata,
+	})
+	if err != nil {
+		return fmt.Errorf("render %q output: %w", cfg.Format, err)
+	}
+
+	if err := writeFile(cfg.OutputFile, rendered); err != nil {
+		return fmt.Errorf("write --output-file %q: %w", cfg.OutputFile, err)
+	}
+
+	return nil
+}
+
+func writeFile(path string, content string) (err error) {
+	file, err := os.Create(path)
+	if err != nil {
+		return fmt.Errorf("create %q: %w", path, err)
+	}
+	defer func() {
+		closeErr := file.Close()
+		if err == nil && closeErr != nil {
+			err = fmt.Errorf("close %q: %w", path, closeErr)
+		}
+	}()
+
+	if _, err := file.WriteString(content); err != nil {
+		return fmt.Errorf("write %q: %w", path, err)
+	}
+	return nil
+}