fix: derive stream status from error traces and seed from source state

- Engine derives stream status from trace/error failure_type (only
  overrides non-complete streams) — no extra source messages needed
- Seed streamStatus from source state on resume so streams the source
  skips (already complete/errored) show correct status in progress

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

Author: tonyxiao

apps/engine/src/lib/progress.ts

@@ -61,13 +61,20 @@ export function trackProgress(opts: {
     let stateCheckpointCount = 0
     const streamStatus = new Map<string, Status>()
 
-    // Restore stream statuses from persisted engine state
+    // Restore stream statuses: engine state first, then source state overrides
+    // (source state is authoritative — streams the source skips emit no messages)
     if (opts.initial_state?.engine?.streams) {
       for (const [stream, data] of Object.entries(opts.initial_state.engine.streams)) {
         const status = (data as { status?: Status })?.status
         if (status) streamStatus.set(stream, status)
       }
     }
+    if (opts.initial_state?.source?.streams) {
+      for (const [stream, data] of Object.entries(opts.initial_state.source.streams)) {
+        const status = (data as { status?: string })?.status
+        if (status) streamStatus.set(stream, status as Status)
+      }
+    }
     const streamErrors = new Map<string, StreamError[]>()
     const hadInitialState = opts.initial_state != null
     const finalState: SyncState = structuredClone(opts.initial_state ?? emptySyncState())
@@ -263,6 +270,9 @@ export function trackProgress(opts: {
             const errs = streamErrors.get(err.stream) ?? []
             errs.push({ message: err.message, failure_type: err.failure_type as FailureType })
             streamErrors.set(err.stream, errs)
+            if (err.failure_type && streamStatus.get(err.stream) !== 'complete') {
+              streamStatus.set(err.stream, err.failure_type as Status)
+            }
           }
         }
       }