Retry and split transient D1 writes

[seveibar]

Summary

• Retry failed Wrangler D1 commands with exponential backoff.
• Capture Wrangler stderr so remote failures include actionable diagnostics.
• If a 50-row footprinter upsert still fails, retry it as smaller sub-batches and leave only exhausted rows eligible for a future run instead of aborting the population.
• Add unit coverage for retry, split, and exhausted-fallback behavior.

Why

Run #31931087288 stopped after about 24 minutes when a remote 50-row D1 write stalled and Wrangler exited with code 1. The population had already processed 1,200 components, and the final row-count report succeeded, so this was a transient write-path failure rather than an EasyEDA conversion failure.

Validation

• Root suite: 226 tests passed.
• Cloudflare proxy suite: 150 tests passed.
• TypeScript check: passed.
• Diff check: passed.