refactor(copilot): use toError in remaining otel/finalize sites

Replace the last two `error instanceof Error ? error : new Error(String(error))`
patterns with toError from @sim/utils/errors. Completes the sweep of clean
candidates — no behavior change.

apps/sim/lib/copilot/request/lifecycle/finalize.ts

@@ -64,7 +64,7 @@ export async function finalizeStream(
       span.setStatus({ code: SpanStatusCode.OK })
     }
   } catch (error) {
-    span.recordException(error instanceof Error ? error : new Error(String(error)))
+    span.recordException(toError(error))
     span.setStatus({ code: SpanStatusCode.ERROR, message: 'finalize threw' })
     throw error
   } finally {

apps/sim/lib/copilot/request/otel.ts

@@ -10,6 +10,7 @@ import {
   TraceFlags,
   trace,
 } from '@opentelemetry/api'
+import { toError } from '@sim/utils/errors'
 import { RequestTraceV1Outcome } from '@/lib/copilot/generated/request-trace-v1'
 import {
   CopilotBranchKind,
@@ -92,12 +93,12 @@ export function isActionableErrorStatus(code: number): boolean {
 // client disconnect, internal timeout, uncategorized AbortError —
 // becomes a real error that the dashboards will surface.
 export function markSpanForError(span: Span, error: unknown): void {
-  const asError = error instanceof Error ? error : new Error(String(error))
+  const asError = toError(error)
   span.recordException(asError)
   if (!isExplicitUserStopError(error)) {
     span.setStatus({
       code: SpanStatusCode.ERROR,
-      message: error instanceof Error ? error.message : String(error),
+      message: asError.message,
     })
   }
 }