Fix ticket 041 merge conflict: update declared_value_kind for ticket 037's param shape

The 041 branch was built against the pre-037 ParamRole/inline-params shape;
rebase the string-kind lookup and test helper onto the unified
ParamDeclaration/label_params/value_param model from ticket 037.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

src/engine.rs

@@ -1322,11 +1322,16 @@ fn declared_value_kind(
     metric_name: &str,
 ) -> Option<MetricPrimitiveKind> {
     match index.get(&IndexKey::MetricDeclaration { name: metric_name.to_string() }) {
-        Some(DataValue::MetricDeclaration { params, .. }) => Some(
-            params
-                .iter()
-                .find(|param| param.role == ParamRole::Value)
-                .map(|param| param.kind)
+        Some(DataValue::MetricDeclaration { value_param, .. }) => Some(
+            value_param
+                .as_ref()
+                .and_then(|name| {
+                    index.get(&IndexKey::ParamDeclaration { name: name.clone() })
+                })
+                .map(|value| match value {
+                    DataValue::ParamDeclaration(param) => param.kind,
+                    _ => MetricPrimitiveKind::Number,
+                })
                 .unwrap_or(MetricPrimitiveKind::Number),
         ),
         _ => None,
@@ -2057,12 +2062,20 @@ mod tests {
     /// Declares a metric whose captured `status` param is `String`-kind and holds the `Value` role,
     /// so every bucket entry for it is a `MetricPrimitive::String` rather than the default occurrence marker.
     fn declare_string_valued_metric(index: &mut BTreeMap<IndexKey, DataValue>) {
+        declare_test_param(
+            index,
+            "status",
+            r"request status=(?P<status>\S+)",
+            "status",
+            MetricPrimitiveKind::String,
+        );
         declare_metric(
             index,
-            metric_request_with_roles(
+            metric_request_with_value(
                 "statuses",
                 r"request status=(?P<status>\S+)",
-                vec![("status", "status", MetricPrimitiveKind::String, ParamRole::Value)],
+                vec![],
+                Some("status"),
             ),
         )
         .unwrap();