feat: scaffold go-html module with Node interface

Introduces the go-html module with a Node rendering interface, Raw and El
constructors, void element handling, and attribute escaping. Includes a
minimal Context stub and tests for all node types.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

context.go

@@ -0,0 +1,15 @@
+package html
+
+// Context carries rendering state through the node tree.
+type Context struct {
+	Identity string
+	Locale   string
+	Data     map[string]any
+}
+
+// NewContext creates a new rendering context with sensible defaults.
+func NewContext() *Context {
+	return &Context{
+		Data: make(map[string]any),
+	}
+}

go.mod

@@ -0,0 +1,5 @@
+module forge.lthn.ai/core/go-html
+
+go 1.25.5
+
+replace forge.lthn.ai/core/go-i18n => ../go-i18n

node.go

@@ -0,0 +1,98 @@
+package html
+
+import "strings"
+
+// Node is anything renderable.
+type Node interface {
+	Render(ctx *Context) string
+}
+
+// voidElements is the set of HTML elements that must not have a closing tag.
+var voidElements = map[string]bool{
+	"area":   true,
+	"base":   true,
+	"br":     true,
+	"col":    true,
+	"embed":  true,
+	"hr":     true,
+	"img":    true,
+	"input":  true,
+	"link":   true,
+	"meta":   true,
+	"source": true,
+	"track":  true,
+	"wbr":    true,
+}
+
+// escapeAttr escapes a string for use in an HTML attribute value.
+func escapeAttr(s string) string {
+	s = strings.ReplaceAll(s, "&", "&")
+	s = strings.ReplaceAll(s, "\"", """)
+	s = strings.ReplaceAll(s, "'", "'")
+	s = strings.ReplaceAll(s, "<", "&lt;")
+	s = strings.ReplaceAll(s, ">", "&gt;")
+	return s
+}
+
+// --- rawNode ---
+
+type rawNode struct {
+	content string
+}
+
+// Raw creates a node that renders without escaping (escape hatch for trusted content).
+func Raw(content string) Node {
+	return &rawNode{content: content}
+}
+
+func (n *rawNode) Render(_ *Context) string {
+	return n.content
+}
+
+// --- elNode ---
+
+type elNode struct {
+	tag      string
+	children []Node
+	attrs    map[string]string
+}
+
+// El creates an HTML element node with children.
+func El(tag string, children ...Node) Node {
+	return &elNode{
+		tag:      tag,
+		children: children,
+		attrs:    make(map[string]string),
+	}
+}
+
+func (n *elNode) Render(ctx *Context) string {
+	var b strings.Builder
+
+	b.WriteByte('<')
+	b.WriteString(n.tag)
+
+	for key, val := range n.attrs {
+		b.WriteByte(' ')
+		b.WriteString(key)
+		b.WriteString(`="`)
+		b.WriteString(escapeAttr(val))
+		b.WriteByte('"')
+	}
+
+	b.WriteByte('>')
+
+	if voidElements[n.tag] {
+		return b.String()
+	}
+
+	for _, child := range n.children {
+		b.WriteString(child.Render(ctx))
+	}
+
+	b.WriteString("</")
+	b.WriteString(n.tag)
+	b.WriteByte('>')
+
+	return b.String()
+}

node_test.go

@@ -0,0 +1,52 @@
+package html
+
+import "testing"
+
+func TestRawNode_Render(t *testing.T) {
+	ctx := NewContext()
+	node := Raw("hello")
+	got := node.Render(ctx)
+	if got != "hello" {
+		t.Errorf("Raw(\"hello\").Render() = %q, want %q", got, "hello")
+	}
+}
+
+func TestElNode_Render(t *testing.T) {
+	ctx := NewContext()
+	node := El("div", Raw("content"))
+	got := node.Render(ctx)
+	want := "<div>content</div>"
+	if got != want {
+		t.Errorf("El(\"div\", Raw(\"content\")).Render() = %q, want %q", got, want)
+	}
+}
+
+func TestElNode_Nested(t *testing.T) {
+	ctx := NewContext()
+	node := El("div", El("span", Raw("inner")))
+	got := node.Render(ctx)
+	want := "<div><span>inner</span></div>"
+	if got != want {
+		t.Errorf("nested El().Render() = %q, want %q", got, want)
+	}
+}
+
+func TestElNode_MultipleChildren(t *testing.T) {
+	ctx := NewContext()
+	node := El("div", Raw("a"), Raw("b"))
+	got := node.Render(ctx)
+	want := "<div>ab</div>"
+	if got != want {
+		t.Errorf("El with multiple children = %q, want %q", got, want)
+	}
+}
+
+func TestElNode_VoidElement(t *testing.T) {
+	ctx := NewContext()
+	node := El("br")
+	got := node.Render(ctx)
+	want := "<br>"
+	if got != want {
+		t.Errorf("El(\"br\").Render() = %q, want %q", got, want)
+	}
+}