Sources: accepted-duplicate % (curation-quality signal)

Per Codex's optional note: alongside the ingest-wide duplicate_rate, expose
accepted_dup_rate — of what a source got ACCEPTED, how much was a duplicate of
already-served content (accepted_total − served). Nearly free (derived from
existing counts); surfaced as a tooltip on the Dup column so the table stays
uncluttered.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/queries.py

@@ -320,8 +320,12 @@ def source_health(conn: sqlite3.Connection) -> list[dict]:
     for r in rows:
         d = dict(r)
         total = d["total_articles"] or 0
-        d["acceptance_rate"] = round(100 * d["accepted_total"] / total) if total else None
+        accepted = d["accepted_total"] or 0
+        d["acceptance_rate"] = round(100 * accepted / total) if total else None
         d["duplicate_rate"] = round(100 * d["duplicates"] / total) if total else None
+        # Curation quality: of what this source got ACCEPTED, how much was a
+        # duplicate of content already served (accepted_total − served = accepted dupes).
+        d["accepted_dup_rate"] = round(100 * (accepted - d["served"]) / accepted) if accepted else None
         out.append(d)
     return out