merge: R-D (citing-coverage warning in graph report)

docs/audit/DATA-QUALITY-2026-06-15.md

@@ -462,7 +462,23 @@ is self-contained so a cold session can pick it up.
 - **Acceptance:** `section` column gains signal (fewer `body`-only); DQ-3 coverage
   vs source improves; no regression in the F-16 quality gate.
 
-### R-D — F-15: warn on low *citing-paper* coverage, not just paper count · **SMALL**
+### R-D — F-15: warn on low *citing-paper* coverage, not just paper count · **DONE 2026-06-17**
+
+**Resolution (what was done):**
+- Added `graph.citing_coverage(graph, known_ids)` → `(papers_with_out_edges,
+  total)`, a `graph_min_citing_coverage` setting (default 0.8), and wired both into
+  `codex graph report`: it now prints `Citing coverage: N/M papers with out-edges
+  (P%)` (and in `--json`), and emits a `Warning` when the share is below the
+  threshold ("low citing coverage weakens PageRank/coupling"). Separate from the
+  existing `graph_min_corpus_size` (total-count) warning.
+- Tests: `citing_coverage` unit tests + CLI tests (line shown; warning fires at
+  low coverage; suppressed at 100%; JSON field). Full suite green; ruff/mypy clean.
+- **Live:** `codex graph report` on the corpus prints `Citing coverage: 29/29
+  papers with out-edges (100%)` with no warning (post-R-A). Branch
+  `feat/graph-coverage-warning`. Files: `codex/config.py`, `codex/graph.py`,
+  `codex/cli.py`, + tests.
+
+**Original plan (for context):**
 - **What:** the open DQ-1 sub-item: `graph_min_corpus_size` only flags total paper
   count. Add a warning when the share of papers with ≥1 out-edge is low (e.g.
   < 80%), since that is what actually starves PageRank/coupling.