feat(style): generate checked class tokens

Add a boring CSS/SCSS class-token surface: slhx-build discovers static class tokens from hemplate/templates/stylesheets and emits generated CssClass constants. Add CssClasses for hemplate +class/view data and migrate techdemo dynamic/effect fragments toward hemplate-owned views with DOM-aware assertions.

req: style/001

req: style/002

req: style/003

req: html_safety/002

req: view/001

req: test/005

slhx-core/src/lib.rs

@@ -143,6 +143,85 @@ impl SafeHtml {
     }
 }
 
+/// A generated, checked CSS class token.
+///
+/// Plain CSS/SCSS owns appearance; slhx only gives Rust a typed reference to
+/// class names discovered from build inputs. req: style/001
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub struct CssClass {
+    name: &'static str,
+}
+
+impl CssClass {
+    pub const fn new(name: &'static str) -> Self {
+        Self { name }
+    }
+
+    pub const fn as_str(self) -> &'static str {
+        self.name
+    }
+}
+
+impl AsRef<str> for CssClass {
+    fn as_ref(&self) -> &str {
+        self.name
+    }
+}
+
+impl core::fmt::Display for CssClass {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.name)
+    }
+}
+
+/// A small displayable list of generated CSS class tokens for hemplate `+class`.
+/// req: style/003
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+pub struct CssClasses {
+    names: String,
+}
+
+impl CssClasses {
+    pub fn new(classes: impl IntoIterator<Item = CssClass>) -> Self {
+        let mut names = String::new();
+        for class in classes {
+            if !names.is_empty() {
+                names.push(' ');
+            }
+            names.push_str(class.as_str());
+        }
+        Self { names }
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.names
+    }
+}
+
+impl From<CssClass> for CssClasses {
+    fn from(class: CssClass) -> Self {
+        Self::new([class])
+    }
+}
+
+impl<const N: usize> From<[CssClass; N]> for CssClasses {
+    fn from(classes: [CssClass; N]) -> Self {
+        Self::new(classes)
+    }
+}
+
+impl AsRef<str> for CssClasses {
+    fn as_ref(&self) -> &str {
+        self.as_str()
+    }
+}
+
+impl core::fmt::Display for CssClasses {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(&self.names)
+    }
+}
+
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 pub struct FormContract {
     pub fields: &'static [FormField],