[web-shared][web] Fix trace viewer pagination issues

[karthikscale3]

Changes

This PR fixes trace viewer pagination so spans and events stay in sync as data loads incrementally.
Instead of loading a limited upfront set, the trace now loads in 50-span batches and fetches additional data as the user scrolls vertically, including the corresponding events for newly loaded spans.

What changed

• Added incremental trace data loading in useWorkflowTraceViewerData:
  • initial load: 50 steps/hooks/events
  • loadMoreTraceData() for next 50-item batch
  • tracking: hasMoreTraceData and isLoadingMoreTraceData
• Ensured events are loaded for newly paged spans (step/hook correlation IDs), so visible spans don’t miss event data.
• Wired scroll-triggered pagination in WorkflowTraceViewer to request the next batch near the bottom of the trace timeline.
• Passed pagination handlers/state through run-detail-view and shared trace wrappers.

Test added

• Added a new nextjs-turbopack workflow example: twoHundredStepsWorkflow (workflows/96_many_steps.ts) that executes 200 sequential steps.
• Used this workflow to validate that:
  • spans beyond the first page load while scrolling,
  • event data appears for newly visible spans without requiring a tab switch.