Fix empty-status backward-compat bug, add From<&StageUsage> for Usage

- Fix: empty-string status from old logs now defaults to "success"
  instead of rendering as red/error
- Add From<&StageUsage> for fabro_llm::Usage to centralize conversion
- Simplify usage aggregation: replace collect+reduce+unwrap with
  direct .reduce() on the iterator

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/crates/fabro-workflows/src/cli/logs.rs

@@ -214,7 +214,10 @@ pub fn format_event_pretty(line: &str, styles: &fabro_util::terminal::Styles) ->
 
         "WorkflowRunCompleted" => {
             let duration = format_duration_ms(envelope.get("duration_ms"));
-            let status_str = str_field(&envelope, "status").unwrap_or("success");
+            let status_str = match str_field(&envelope, "status") {
+                Some(s) if !s.is_empty() => s,
+                _ => "success",
+            };
             let status_upper = status_str.to_uppercase();
             let status_style = match status_str {
                 "success" | "partial_success" => &styles.bold_green,

lib/crates/fabro-workflows/src/engine.rs

@@ -2144,28 +2144,10 @@ impl WorkflowRunEngine {
             .cloned()
             .unwrap_or_else(Outcome::success);
 
-        let run_usage: Option<fabro_llm::types::Usage> = {
-            let usages: Vec<fabro_llm::types::Usage> = node_outcomes
-                .values()
-                .filter_map(|o| {
-                    let u = o.usage.as_ref()?;
-                    Some(fabro_llm::types::Usage {
-                        input_tokens: u.input_tokens,
-                        output_tokens: u.output_tokens,
-                        total_tokens: u.input_tokens + u.output_tokens,
-                        cache_read_tokens: u.cache_read_tokens,
-                        cache_write_tokens: u.cache_write_tokens,
-                        reasoning_tokens: u.reasoning_tokens,
-                        raw: None,
-                    })
-                })
-                .collect();
-            if usages.is_empty() {
-                None
-            } else {
-                Some(usages.into_iter().reduce(|a, b| a + b).unwrap())
-            }
-        };
+        let run_usage: Option<fabro_llm::types::Usage> = node_outcomes
+            .values()
+            .filter_map(|o| o.usage.as_ref().map(fabro_llm::types::Usage::from))
+            .reduce(|a, b| a + b);
 
         self.services
             .emitter

lib/crates/fabro-workflows/src/outcome.rs

@@ -61,6 +61,20 @@ pub struct StageUsage {
     pub cost: Option<f64>,
 }
 
+impl From<&StageUsage> for fabro_llm::types::Usage {
+    fn from(u: &StageUsage) -> Self {
+        Self {
+            input_tokens: u.input_tokens,
+            output_tokens: u.output_tokens,
+            total_tokens: u.input_tokens + u.output_tokens,
+            cache_read_tokens: u.cache_read_tokens,
+            cache_write_tokens: u.cache_write_tokens,
+            reasoning_tokens: u.reasoning_tokens,
+            raw: None,
+        }
+    }
+}
+
 /// Structured failure information carried through the pipeline.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct FailureDetail {