extract TokenUsage::from_stream_event helper to keep run_claude under clippy line limit

hive-ag3nt/src/events.rs

@@ -171,6 +171,24 @@ impl TokenUsage {
     pub fn context_tokens(&self) -> u64 {
         self.input_tokens + self.cache_read_input_tokens + self.cache_creation_input_tokens
     }
+
+    /// Parse usage from a stream-json event. Returns `Some` only for the
+    /// terminal `result` event (which is the only one that carries `usage`);
+    /// every other event maps to `None`. Missing numeric fields default to 0
+    /// so partial server payloads don't drop the whole snapshot.
+    pub fn from_stream_event(v: &serde_json::Value) -> Option<Self> {
+        if v.get("type").and_then(|t| t.as_str()) != Some("result") {
+            return None;
+        }
+        let u = v.get("usage")?;
+        let field = |k: &str| u.get(k).and_then(serde_json::Value::as_u64).unwrap_or(0);
+        Some(Self {
+            input_tokens: field("input_tokens"),
+            output_tokens: field("output_tokens"),
+            cache_read_input_tokens: field("cache_read_input_tokens"),
+            cache_creation_input_tokens: field("cache_creation_input_tokens"),
+        })
+    }
 }
 
 /// Authoritative turn-loop state. The harness owns it; the web UI