Add batch progress, cancel, retry, and per-item failure reporting

[09ashishkapoor]

Summary

Add batch progress, cancel, retry, and per-item failure reporting for larger jobs.

Source

Derived from docs/ROADMAP.md (Phase 3 — Package and polish for real-world batch use).

Goal

Make larger export jobs more dependable and easier to control.

Suggested scope

• Visible batch progress updates
• Cancel support
• Retry support
• Per-item failure reporting and summaries

Notes

This issue was generated from the roadmap for tracking. Refine acceptance criteria during implementation if needed.

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