Gate 4: satisfy UAPI observability typecheck

Normalize PTRR step-id parsing so the stricter UAPI TypeScript build receives a concrete string before checking Reading pipeline telemetry step names.

Validation: pnpm -C uapi exec tsc --noEmit; pnpm run check:v29-gate4; pnpm --dir uapi exec jest --runTestsByPath tests/terminalPipelineHarnessClient.test.ts tests/pipelineExecutionLogHeader.test.tsx --runInBand; pnpm exec eslint packages/pipelines/asset-pack/src/reading-pipeline-observability.ts uapi/app/terminal/terminal-pipeline-harness-client.ts uapi/components/base/bitcode/execution/pipeline-execution-log-header.tsx uapi/components/base/bitcode/execution/pipeline-execution-log.tsx --ext .ts,.tsx; git diff --check

Author: geraldarthurdavis

packages/pipelines/asset-pack/src/reading-pipeline-observability.ts

@@ -464,7 +464,7 @@ function inferPipelineName(source: ProjectionSource): ReadingPipelineName | null
 }
 
 function stepNameFromId(value: unknown): ReadingPipelinePtrrStepName | null {
-  const text = String(value || '').split('.').pop();
+  const text = String(value || '').split('.').pop() || '';
   return ['plan', 'try', 'refine', 'retry'].includes(text)
     ? (text as ReadingPipelinePtrrStepName)
     : null;