news archive: keep every headline + its DeepSeek score in its own DB

Headlines only ever survived as a side effect of signal logging, and
logs/signals.db was rotated around 2026-09-04 — destroying the 3-week,
4,054-headline corpus news_sentiment_value_2026-09-04.md was written on.
logs/ is gitignored, so git could not recover it and nobody noticed for
four days. There is no way to backfill a fetch window once it passes.

news_archive.py writes to its OWN database (logs/newsdata.db) so a
signal-log rotation cannot take the news with it. One row per distinct
headline (sha256 key) with the text, description, link, publisher,
publish time, the score, and — new — which scorer produced that score.

Provenance is the load-bearing part. DeepSeek scores 78/78 on the
2026-08-06 golden set; the keyword scorer it overrides scores 24/78
(31%), and that is what silently stands on no key, disabled, daily cap,
timeout, HTTP/parse failure, or the >25-new-headlines-per-cycle batch
overflow. Until now both landed in the same column, indistinguishable,
so a model trained on the mix would inherit the keyword scorer's errors.
NewsSentiment.score_source now records it, mirrored into signals.db via
signal_log._headline_to_dict, and teacher_model/teacher_prompt_sha1 keep
labels made under a changed prompt from being pooled with older ones.

Writes are one atomic UPSERT per row, upgrade-only: an llm score always
replaces a keyword one (the batch-overflow tail gets labelled on the
next window in a long-running process — verified 13/13), a keyword score
never overwrites an llm one, and re-seeing a headline always counts. A
read-then-write pair lost increments when the bot, the dashboard
publisher and the tests first saw a headline together, and the WAL
switch itself needed _with_lock_retry; both are regression-tested with
three concurrent writers.

The hook sits at the end of _fetch_news_sentiment_raw, BEFORE
_is_neutral_headline runs in get_fundamental_context. Archiving
downstream of that ±0.1 filter is why signals.db holds almost no neutral
headlines and would have taught a trained scorer that "neutral" barely
exists.

scripts/backfill_news_archive.py seeds it from both DB shapes on disk,
read-only and idempotent, recomputing provenance by comparing each
stored score against the keyword scorer (neither source recorded it):
1,016 distinct headlines, 846 DeepSeek-labelled, growing ~1,400/week.

Nothing in the signal core changed. Both news gating flags stay False,
no gate reads any of this, and the backtester never builds a NewsEngine
so replays never archive (test-locked). 468 -> 483 tests, including a
new guard that AST-walks live code for sklearn/scipy/lightgbm imports —
that check did not exist before.

Do not train yet: ~800 labels gives a holdout too small to grade
(SE +/-0.032). Target is ~4,000 deduplicated headlines over >=3 weeks.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bzv4ETVapFNauFDQht7QtA

signal_log.py

@@ -573,6 +573,10 @@ def _headline_to_dict(h: Any) -> Dict[str, Any]:
         "link": getattr(h, "link", None),
         "description": getattr(h, "description", None),
         "publisher": getattr(h, "publisher", None),
+        # Which scorer produced "score": "keyword" | "llm" | "model".
+        # The durable corpus lives in news_archive.py; this mirrors the
+        # provenance here so signals.db rows are self-describing too.
+        "score_source": getattr(h, "score_source", None),
     }