♻️ (html): Añade valores extra a Props

- Reordena campos, variantes y métodos para mayor consistencia interna.
- Añade `extra_or`, `extra_or_default` y `extra_or_else` a `Props`.
- Mejora la documentación y amplía los tests de integración.

tests/html_props_extras.rs

@@ -0,0 +1,120 @@
+use pagetop::prelude::*;
+
+// **< PropsOp::set_extra / remove_extra >**********************************************************
+
+#[pagetop::test]
+async fn set_and_read_extra() {
+    let props = Props::default().with_prop(PropsOp::set_extra("ext.flag", true));
+    assert_eq!(*props.extra::<bool>("ext.flag").unwrap(), true);
+}
+
+#[pagetop::test]
+async fn overwrite_extra() {
+    let props = Props::default()
+        .with_prop(PropsOp::set_extra("ext.count", 1_u32))
+        .with_prop(PropsOp::set_extra("ext.count", 2_u32));
+    assert_eq!(*props.extra::<u32>("ext.count").unwrap(), 2);
+}
+
+#[pagetop::test]
+async fn remove_extra() {
+    let props = Props::default()
+        .with_prop(PropsOp::set_extra("ext.flag", true))
+        .with_prop(PropsOp::remove_extra("ext.flag"));
+    assert_eq!(
+        props.extra::<bool>("ext.flag"),
+        Err(PropsError::ExtraNotFound { key: "ext.flag" })
+    );
+}
+
+// **< Props::extra >*******************************************************************************
+
+#[pagetop::test]
+async fn extra_not_found() {
+    let props = Props::default();
+    assert_eq!(
+        props.extra::<bool>("ext.missing"),
+        Err(PropsError::ExtraNotFound { key: "ext.missing" })
+    );
+}
+
+#[pagetop::test]
+async fn extra_type_mismatch() {
+    let props = Props::default().with_prop(PropsOp::set_extra("ext.flag", true));
+    assert!(matches!(
+        props.extra::<u32>("ext.flag"),
+        Err(PropsError::ExtraTypeMismatch { .. })
+    ));
+}
+
+// **< Props::extra_or >****************************************************************************
+
+#[pagetop::test]
+async fn extra_or_returns_value_when_found() {
+    let props = Props::default().with_prop(PropsOp::set_extra("ext.flag", true));
+    assert_eq!(props.extra_or("ext.flag", false), true);
+}
+
+#[pagetop::test]
+async fn extra_or_returns_default_on_missing() {
+    let props = Props::default();
+    assert_eq!(props.extra_or("ext.flag", false), false);
+}
+
+#[pagetop::test]
+async fn extra_or_returns_default_on_type_mismatch() {
+    let props = Props::default().with_prop(PropsOp::set_extra("ext.flag", true));
+    assert_eq!(props.extra_or("ext.flag", 0_u32), 0_u32);
+}
+
+// **< Props::extra_or_default >********************************************************************
+
+#[pagetop::test]
+async fn extra_or_default_returns_type_default_on_missing() {
+    let props = Props::default();
+    assert_eq!(props.extra_or_default::<bool>("ext.flag"), false);
+    assert_eq!(props.extra_or_default::<i32>("ext.count"), 0);
+}
+
+// **< Props::extra_or_else >***********************************************************************
+
+#[pagetop::test]
+async fn extra_or_else_calls_closure_on_missing() {
+    let props = Props::default();
+    assert_eq!(
+        props.extra_or_else("ext.label", || "fallback".to_string()),
+        "fallback"
+    );
+}
+
+// **< Clone and mixed types >**********************************************************************
+
+#[pagetop::test]
+async fn clone_preserves_extras() {
+    let props = Props::default().with_prop(PropsOp::set_extra("ext.flag", true));
+    let cloned = props.clone();
+    assert_eq!(*cloned.extra::<bool>("ext.flag").unwrap(), true);
+}
+
+#[pagetop::test]
+async fn multiple_extras_with_different_types() {
+    let props = Props::default()
+        .with_prop(PropsOp::set_extra("ext.flag", true))
+        .with_prop(PropsOp::set_extra("ext.count", 42_u32))
+        .with_prop(PropsOp::set_extra("ext.label", "hello".to_string()));
+
+    assert_eq!(*props.extra::<bool>("ext.flag").unwrap(), true);
+    assert_eq!(*props.extra::<u32>("ext.count").unwrap(), 42);
+    assert_eq!(props.extra::<String>("ext.label").unwrap(), "hello");
+}
+
+#[pagetop::test]
+async fn extras_not_emitted_in_html() {
+    let props = Props::default()
+        .with_prop(PropsOp::set_extra("ext.flag", true))
+        .with_prop(PropsOp::add_classes("btn"));
+    assert_eq!(
+        html! { button (props) { "OK" } }.into_string(),
+        r#"<button class="btn">OK</button>"#
+    );
+}