Curation v2 step 5: deep assessment, utility, diversified shortlist

assess.rs replaces score.rs (DEEP_INSTRUCTIONS, representative sample
with [BEGINNING]/[MIDDLE]/[END], facets, cached deep rows with --rescore
bypass), rank.rs adds the utility blend over present signals with gate
ramps and the leader-clustered shortlist (cap 2 → 3 → uncapped, protected
top-N, exploration reserve), editor.rs replaces select.rs with the §13
rendering and utility-ordered fallbacks. ScoredArticle is gone; Candidate
is the only flow type. deep_batch_size replaces score_batch_size.

Started by Codex (cut off by its usage limit mid-verification) and
finished by a Claude agent from docs/plans/curation-v2-briefs/step5.md;
reviewed against plan §12–§13.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A1rCLQeKBgnBo3oTgHuTMe

config.example.toml

@@ -36,9 +36,9 @@ page_limit = 250
 base_url = "https://api.deepseek.com/v1"
 model = "deepseek-v4-flash"          # DeepSeek-V4-Flash-0731 (confirmed 2026-08-15)
 # api_key via DAILY_EPUB_DEEPSEEK__API_KEY env
-score_batch_size = 12
+deep_batch_size = 8                  # articles per close-reading assessment request
 triage_batch_size = 25               # articles per first-pass triage request
-max_concurrent_requests = 4          # triage and stage-A batches in flight at once
+max_concurrent_requests = 4          # triage and deep-assessment batches in flight
 score_temperature = 0.3
 editorial_temperature = 0.8          # used only when DeepSeek is the fallback editor
 # USD per 1M tokens, used for the cost guardrail.