Add minimal batch output with --batch-full-output opt-in

[dnagoda]

📚 Stack (bottom → top)

1. Add batch mode for processing multiple inputs via JSONL #1 Add batch mode for processing multiple inputs via JSONL
2. Preserve JSON input object order #2 Preserve JSON input object order
3. Refine batch failure handling #3 Refine batch failure handling
4. Reuse the compiled provider across runs #4 Reuse the compiled provider across runs
5. Compute humanized bytes lazily #5 Compute humanized bytes lazily
6. Add minimal batch output with --batch-full-output opt-in #6 Add minimal batch output with --batch-full-output opt-in

Stacked draft PRs on the fork; review bottom-up. Merge target is Shopify/function-runner once upstream write access is available.

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Why

Batch mode emitted the full FunctionRunResult per input — including the echoed
input, function name, and size. Parity replay only needs the run outcome, and
the extra fields bloat the JSONL output for large runs.

What

• Default batch output is now a minimal record per line:
  success, instructions, memory_usage, logs, output.
• Add --batch-full-output to opt back into the complete FunctionRunResult
  per line.
• Extend integration coverage for both the minimal default and the
  full-output flag.

Single-run output is unaffected.

Testing

• cargo test batch_
• cargo test

[dnagoda]

Moved upstream to Shopify#594 now that write access is available. Closing this fork PR.