feat(build): emit checked param tokens

Generate ParamName constants for handle data parameters so public code can refer to checked param metadata instead of stringly typed names.

req: codegen/003

slhx-core/src/lib.rs

@@ -186,6 +186,35 @@ impl core::fmt::Display for CssClass {
     }
 }
 
+/// A generated, checked parameter token.
+/// req: codegen/003
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+pub struct ParamName {
+    name: &'static str,
+}
+
+impl ParamName {
+    pub const fn new(name: &'static str) -> Self {
+        Self { name }
+    }
+
+    pub const fn as_str(self) -> &'static str {
+        self.name
+    }
+}
+
+impl AsRef<str> for ParamName {
+    fn as_ref(&self) -> &str {
+        self.name
+    }
+}
+
+impl core::fmt::Display for ParamName {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.write_str(self.name)
+    }
+}
+
 /// A generated, checked component token.
 /// req: component/003
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]