When a harvest produced 15+ articles, asking the agent to emit the entire
.summaries.json in a single response hit the model's output-token ceiling —
the response was truncated and the tail articles silently got no summary
(their 原文 kept the __SUMMARY_<slug>__ sentinel forever). Reproduced every
time a high-volume source ran; ≤9-article sources never hit it.

Add scripts/summary-add.js to incrementally merge small batches (≤4) into
.summaries.json (keyed by url, overwrite-no-dup), with a --status mode that
diffs manifest vs summaries so interrupted runs can resume. Rewrite SKILL.md
Flow A Step 2 + Guardrails to mandate batching, and surface a batchHint in
harvest.js's manifest so the agent sees the guidance on first contact.