fix(usage): prevent detail view from overriding active request status

- Keep pending/streaming lifecycle status authoritative for active requests
- Prevent detail status code or trace state from misclassifying in-flight requests as stream/failed
- Add regression coverage for status resolution and timeline state emission

frontend/src/features/usage/utils/__tests__/status.spec.ts

@@ -141,6 +141,25 @@ describe('usage status helpers', () => {
     })).toBe('failed')
   })
 
+  it('keeps active request lifecycle status authoritative over detail status code inference', () => {
+    expect(resolveTimelineFinalStatus({
+      requestStatus: 'streaming',
+      statusCode: 200,
+    })).toBe('streaming')
+
+    expect(resolveTimelineFinalStatus({
+      requestStatus: 'streaming',
+      statusCode: 503,
+      traceFinalStatus: 'failed',
+    })).toBe('streaming')
+
+    expect(resolveTimelineFinalStatus({
+      requestStatus: 'pending',
+      statusCode: 200,
+      traceFinalStatus: 'success',
+    })).toBe('pending')
+  })
+
   it('uses explicit has_fallback flag for transfer filtering', () => {
     expect(hasUsageFallback(buildUsageRecord({ has_fallback: true }))).toBe(true)
     expect(hasUsageFallback(buildUsageRecord({ has_fallback: false }))).toBe(false)

frontend/src/features/usage/utils/status.ts

@@ -295,6 +295,9 @@ export function resolveTimelineFinalStatus(params: {
     }
     return requestStatus
   }
+  if (requestStatus === 'pending' || requestStatus === 'streaming') {
+    return requestStatus
+  }
 
   const traceStatus = normalizeTimelineFinalStatus(params.traceFinalStatus)
   if (traceStatus === 'success' || traceStatus === 'failed' || traceStatus === 'cancelled') {
@@ -304,14 +307,14 @@ export function resolveTimelineFinalStatus(params: {
     return traceStatus
   }
 
-  if (hasTerminalSuccessStatusCode !== undefined) {
-    return hasTerminalSuccessStatusCode ? 'success' : 'failed'
-  }
-
   if (params.hasPendingCandidates) {
     return 'pending'
   }
 
+  if (hasTerminalSuccessStatusCode !== undefined) {
+    return hasTerminalSuccessStatusCode ? 'success' : 'failed'
+  }
+
   if (traceStatus) {
     return traceStatus
   }