6bb5e7ac

By: Nic Fink <n.fink@bluewin.ch>

Fix evaluator stalls; add bulk sample generation and ESS diagnostics

- Preserve batch claims and results across database retries.
- Fence stale claims and isolate completed results by task.
- Correct worker connection budgeting and stale launch reservations.
- Preserve default resource roots and set local PostgreSQL connections to 512.
- Improve queue diagnostics and campaign failure attribution.
- Add normalized ESS using absolute contributions.
- Use numeric sample-count axes and remove empty plot legends.
- Add regression coverage and operational documentation.
- Add independent heatmap limits and selectable zero-origin and linear Viridis scales.
- Default integrand and PDF heatmaps to linear color ranges.
- Add optional bulk sample generation with independent evaluator batching.
- Regroup training results per sampler draw and checkpoint buffered work.
- Expose live bulk-generation tuning and test queue limits, adaptive chunks, and recovery.