type: voice, Requirement.value, playable resource cards

A voice requirement records in the browser and ships PCM to the relay
as one binary frame (voice.js, same mount/stop contract as gesture);
its value becomes {key, digest, duration_ms}. Requirement.value
presets a field and, on a dynamic page, takes the URL segment - so
value: "{key}" tells the voice field where to record. A url resource
source takes the segment too. Resource items with an https `audio`
field render an <audio> player. The gesture widget reports picks to
the relay for ranking.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/content.rs

@@ -439,7 +439,13 @@ pub struct Requirement {
     /// the selected file's current content.
     #[serde(default)]
     pub bind: Option<Bind>,
-    /// `type: gesture` only - ws(s):// URL of a redoal-relay instance
+    /// A preset value the field starts with. On a dynamic page the
+    /// URL segment substitutes into `{name}` placeholders here, like
+    /// resource keys - `value: "{key}"` on a hidden field carries the
+    /// page's key into the answer.
+    #[serde(default)]
+    pub value: Option<String>,
+    /// `type: gesture` / `type: voice` - ws(s):// URL of a redoal-relay instance
     /// the drawing widget connects to for live echoes of similar
     /// strokes. Absent means the widget works offline: the drawn path
     /// still submits, it just never gets a network-computed key or
@@ -817,15 +823,26 @@ pub fn resolve_question(
                     }
                 }
             };
+            // A url source's address takes the segment too:
+            // `https://relay.redoal.com/place/{key}`.
+            let substitute_url = |src: &mut ResourceSource| {
+                if let ResourceSource::Url { url } = src {
+                    for (name, value) in &captures {
+                        *url = url.replace(&format!("{{{name}}}"), value);
+                    }
+                }
+            };
             for alt in &mut resolved.alternatives {
                 for feature in &mut alt.features {
                     if let Some(res) = &mut feature.resource {
                         substitute(&mut res.key);
+                        substitute_url(&mut res.source);
                     }
                     for req in &mut feature.requirements {
                         if let Some(res) = &mut req.resource {
                             substitute(&mut res.key);
                         }
+                        substitute(&mut req.value);
                     }
                 }
             }
@@ -1151,9 +1168,9 @@ pub fn validate_questions(
                         );
                     }
                     if let Some(relay) = &requirement.relay {
-                        if requirement.kind != "gesture" {
+                        if requirement.kind != "gesture" && requirement.kind != "voice" {
                             anyhow::bail!(
-                                "question {:?} alternative {:?} feature {:?}: requirement {:?} declares relay but is type {:?} - relay only makes sense on type: gesture",
+                                "question {:?} alternative {:?} feature {:?}: requirement {:?} declares relay but is type {:?} - relay only makes sense on type: gesture or voice",
                                 question.id, alternative.name, feature.name, requirement.name, requirement.kind
                             );
                         }
@@ -2019,4 +2036,28 @@ alternatives:
         let odd = serde_json::json!({"k": "a/b c"});
         assert_eq!(template_action("/p/{k}", &odd).as_deref(), Some("/p/a-b-c"));
     }
+
+    #[test]
+    fn dynamic_page_fills_requirement_values() {
+        let q: Question = serde_yaml::from_str(
+            "id: /shape/[key]\nname: P\nalternatives:\n  - name: A\n    features:\n      - name: F\n        requirements:\n          - name: key\n            type: hidden\n            value: \"{key}\"\n",
+        )
+        .unwrap();
+        let mut qs = std::collections::HashMap::new();
+        qs.insert(q.id.clone(), q);
+        let page = resolve_question(&qs, "/shape/20aa98").unwrap();
+        assert_eq!(page.alternatives[0].features[0].requirements[0].value.as_deref(), Some("20aa98"));
+
+        let q: Question = serde_yaml::from_str(
+            "id: /shape/[key]\nname: P\nalternatives:\n  - name: A\n    features:\n      - name: F\n        resource:\n          source: { kind: url, url: \"https://relay.example/place/{key}\" }\n          public: true\n",
+        )
+        .unwrap();
+        let mut qs = std::collections::HashMap::new();
+        qs.insert(q.id.clone(), q);
+        let page = resolve_question(&qs, "/shape/20aa98").unwrap();
+        match &page.alternatives[0].features[0].resource.as_ref().unwrap().source {
+            ResourceSource::Url { url } => assert_eq!(url, "https://relay.example/place/20aa98"),
+            _ => panic!(),
+        }
+    }
 }