feat: enhance Html and Http stdlib modules

Html: add RawHtml, Attribute, meta/link/script/iframe/figure/figcaption
elements, attr() helper, rawHtml() helper, seoDocument() for SEO meta
tags, fix document() to use Attribute instead of DataAttr for standard
HTML attributes.

Http: add serveStaticFile(), parseFormBody(), getFormField(),
sendResponse() convenience helpers.

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

stdlib/html.lux

@@ -14,6 +14,7 @@
 pub type Html<M> =
     | Element(String, List<Attr<M>>, List<Html<M>>)
     | Text(String)
+    | RawHtml(String)
     | Empty
 
 // Attributes that can be applied to elements
@@ -41,6 +42,7 @@ pub type Attr<M> =
     | OnKeyDown(fn(String): M)
     | OnKeyUp(fn(String): M)
     | DataAttr(String, String)
+    | Attribute(String, String)
 
 // ============================================================================
 // Element builders - Container elements
@@ -180,6 +182,28 @@ pub fn video<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
 pub fn audio<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
     Element("audio", attrs, children)
 
+// ============================================================================
+// Element builders - Document / Head elements
+// ============================================================================
+
+pub fn meta<M>(attrs: List<Attr<M>>): Html<M> =
+    Element("meta", attrs, [])
+
+pub fn link<M>(attrs: List<Attr<M>>): Html<M> =
+    Element("link", attrs, [])
+
+pub fn script<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
+    Element("script", attrs, children)
+
+pub fn iframe<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
+    Element("iframe", attrs, children)
+
+pub fn figure<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
+    Element("figure", attrs, children)
+
+pub fn figcaption<M>(attrs: List<Attr<M>>, children: List<Html<M>>): Html<M> =
+    Element("figcaption", attrs, children)
+
 // ============================================================================
 // Element builders - Tables
 // ============================================================================
@@ -285,6 +309,12 @@ pub fn onKeyUp<M>(h: fn(String): M): Attr<M> =
 pub fn data<M>(name: String, value: String): Attr<M> =
     DataAttr(name, value)
 
+pub fn attr<M>(name: String, value: String): Attr<M> =
+    Attribute(name, value)
+
+pub fn rawHtml<M>(content: String): Html<M> =
+    RawHtml(content)
+
 // ============================================================================
 // Utility functions
 // ============================================================================
@@ -319,6 +349,7 @@ pub fn renderAttr<M>(attr: Attr<M>): String =
         Checked(false) => "",
         Name(n) => " name=\"" + n + "\"",
         DataAttr(name, value) => " data-" + name + "=\"" + value + "\"",
+        Attribute(name, value) => " " + name + "=\"" + value + "\"",
         // Event handlers are ignored in static rendering
         OnClick(_) => "",
         OnInput(_) => "",
@@ -355,6 +386,7 @@ pub fn render<M>(html: Html<M>): String =
             }
         },
         Text(content) => escapeHtml(content),
+        RawHtml(content) => content,
         Empty => ""
     }
 
@@ -368,15 +400,47 @@ pub fn escapeHtml(s: String): String = {
     s4
 }
 
-// Render a full HTML document
+// Render a full HTML document (basic)
 pub fn document(title: String, headExtra: List<Html<M>>, bodyContent: List<Html<M>>): String = {
     let headElements = List.concat([
-        [Element("meta", [DataAttr("charset", "UTF-8")], [])],
+        [Element("meta", [Attribute("charset", "UTF-8")], [])],
-        [Element("meta", [Name("viewport"), Value("width=device-width, initial-scale=1.0")], [])],
+        [Element("meta", [Name("viewport"), Attribute("content", "width=device-width, initial-scale=1.0")], [])],
         [Element("title", [], [Text(title)])],
         headExtra
     ])
-    let doc = Element("html", [DataAttr("lang", "en")], [
+    let doc = Element("html", [Attribute("lang", "en")], [
+        Element("head", [], headElements),
+        Element("body", [], bodyContent)
+    ])
+    "<!DOCTYPE html>\n" + render(doc)
+}
+
+// Render a full HTML document with SEO meta tags
+pub fn seoDocument(
+    title: String,
+    description: String,
+    url: String,
+    ogImage: String,
+    headExtra: List<Html<M>>,
+    bodyContent: List<Html<M>>
+): String = {
+    let headElements = List.concat([
+        [Element("meta", [Attribute("charset", "UTF-8")], [])],
+        [Element("meta", [Name("viewport"), Attribute("content", "width=device-width, initial-scale=1.0")], [])],
+        [Element("title", [], [Text(title)])],
+        [Element("meta", [Name("description"), Attribute("content", description)], [])],
+        [Element("meta", [Attribute("property", "og:title"), Attribute("content", title)], [])],
+        [Element("meta", [Attribute("property", "og:description"), Attribute("content", description)], [])],
+        [Element("meta", [Attribute("property", "og:type"), Attribute("content", "website")], [])],
+        [Element("meta", [Attribute("property", "og:url"), Attribute("content", url)], [])],
+        [Element("meta", [Attribute("property", "og:image"), Attribute("content", ogImage)], [])],
+        [Element("meta", [Name("twitter:card"), Attribute("content", "summary_large_image")], [])],
+        [Element("meta", [Name("twitter:title"), Attribute("content", title)], [])],
+        [Element("meta", [Name("twitter:description"), Attribute("content", description)], [])],
+        [Element("link", [Attribute("rel", "canonical"), Href(url)], [])],
+        headExtra
+    ])
+    let doc = Element("html", [Attribute("lang", "en")], [
         Element("head", [], headElements),
         Element("body", [], bodyContent)
     ])

stdlib/http.lux

@@ -625,6 +625,41 @@ pub fn router(routes: List<Route>, notFound: fn(Request): Response): Handler =
         }
     }
 
+// ============================================================
+// Static File Serving
+// ============================================================
+
+// Serve a static file from disk
+pub fn serveStaticFile(basePath: String, requestPath: String): Response with {File} = {
+    let filePath = basePath + requestPath
+    if File.exists(filePath) then {
+        let content = File.read(filePath)
+        let mime = getMimeType(filePath)
+        { status: 200, headers: [("Content-Type", mime)], body: content }
+    } else
+        { status: 404, headers: textHeaders(), body: "Not Found" }
+}
+
+// ============================================================
+// Form Body Parsing
+// ============================================================
+
+// Parse URL-encoded form body (same format as query strings)
+pub fn parseFormBody(body: String): List<(String, String)> =
+    parseQueryParams(body)
+
+// Get a form field value by name
+pub fn getFormField(fields: List<(String, String)>, name: String): Option<String> =
+    getParam(fields, name)
+
+// ============================================================
+// Response Helpers
+// ============================================================
+
+// Send a Response using HttpServer effect (convenience wrapper)
+pub fn sendResponse(resp: Response): Unit with {HttpServer} =
+    HttpServer.respondWithHeaders(resp.status, resp.body, resp.headers)
+
 // ============================================================
 // Example Usage
 // ============================================================