Dumb OMO commit

.omo/notepads/news-triage/decisions.md

@@ -188,3 +188,24 @@ _Auto-scaffolded by /start-work. Append new entries below - never overwrite._
   DB column — a direct hand-written match keeps the DB layer decoupled
   from `news_core`'s serde attribute and makes the two directions
   symmetric and easy to audit).
+
+## F2/F3 final-wave fixes — cold-start percentile rule
+
+- **Cold-start rule for trailing-window percentile ranks**: the draft specifies
+  a cold-start fallback only for the relevance *score* (BM25-only until 20
+  feedback samples; `.omo/drafts/news-triage.md:45`), not for percentile ranks.
+  When `PercentileTracker::percentile_rank` returns `StoreError::InsufficientData`
+  because the trailing 7-day window is empty, the scheduler maps it to `0.0`
+  with a one-line `tracing::info!` log.
+- **Rationale**: conservative gate behavior. With percentile ranks at 0.0, no
+  story can meet the notify threshold (relevance @ p90) or digest band
+  [75, 90) until the window has data, preventing bogus batch-local
+  percentiles from driving decisions. The breaking-news bypass lane
+  (`source_count >= 2` or importance @ p99) is unaffected: corroboration bypass
+  is percentile-independent, and the importance percentile uses its own
+  distribution.
+- **JSON boundary for blocklist veto**: `StoryRow.relevance` is `Option<f64>`,
+  mapped with `relevance.is_finite().then_some(relevance)`. This keeps the
+  `f64::NEG_INFINITY` sentinel inside the backend scorer while serializing
+  honestly as JSON `null` at the API boundary. `importance` remains `f64`
+  because it is finite by construction (multi-hot arithmetic, no veto path).