fix(trace): show span IDs in trace view and fix event_id mapping

The trace detail API returns `event_id` instead of `span_id` on each
span, so all span IDs rendered as `undefined` in the span tree and
`span view` lookups always failed. Normalize the response in
`getDetailedTrace` by copying `event_id` → `span_id`, and append the
span ID to each tree line so users can copy it into `span view`.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: betegon

src/lib/api-client.ts

@@ -1503,7 +1503,24 @@ export async function getDetailedTrace(
       },
     }
   );
-  return data;
+  return data.map(normalizeTraceSpan);
+}
+
+/**
+ * The trace detail API (`/trace/{id}/`) returns each span's unique identifier
+ * as `event_id` rather than `span_id`. The value is the same 16-hex-char span
+ * ID that `parent_span_id` references on child spans. We copy it to `span_id`
+ * so the rest of the codebase can use a single, predictable field name.
+ */
+function normalizeTraceSpan(span: TraceSpan): TraceSpan {
+  const normalized = { ...span };
+  if (!normalized.span_id && normalized.event_id) {
+    normalized.span_id = normalized.event_id;
+  }
+  if (normalized.children) {
+    normalized.children = normalized.children.map(normalizeTraceSpan);
+  }
+  return normalized;
 }
 
 /** Fields to request from the transactions API */

src/lib/formatters/human.ts

@@ -1122,6 +1122,8 @@ function formatSpanSimple(span: TraceSpan, opts: FormatSpanOptions): void {
     line += `  ${muted(`(${prettyMs(durationMs)})`)}`;
   }
 
+  line += `  ${muted(span.span_id)}`;
+
   lines.push(line);
 
   if (currentDepth < maxDepth) {