feat(cra): route secure-dev breadth to code_security (atom-grain)

Both network_security and code_security are now atom-grain. Per-sub_topic
use_case routing: secure_development -> code_security (best for secure-dev
findings), everything else -> network_security. Findings carry breadth_use_case
so the source context (which atom corpus) is visible under the best-practice depth.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend-compliance/compliance/services/cra_use_case_controls.py

@@ -38,10 +38,22 @@ _REQ_TO_SUBTOPIC = {
 }
 
 
+# Which atom-grain use_case is most relevant per sub_topic. Both network_security
+# and code_security are atom-grain; secure-dev is best served by code_security.
+_SUBTOPIC_TO_USECASE = {
+    "secure_development": "code_security",
+}
+_DEFAULT_USECASE = "network_security"
+
+
 def subtopic_for(req_id: str):
     return _REQ_TO_SUBTOPIC.get(req_id)
 
 
+def usecase_for(sub_topic: str) -> str:
+    return _SUBTOPIC_TO_USECASE.get(sub_topic, _DEFAULT_USECASE)
+
+
 def enrich_findings_with_breadth(mapped: list, db, limit: int = 5) -> None:
     """Attach `sub_topic` + `regulatory_breadth` (atom controls) to each finding.
 
@@ -55,15 +67,19 @@ def enrich_findings_with_breadth(mapped: list, db, limit: int = 5) -> None:
         m["sub_topic"] = st
         if not st:
             m["regulatory_breadth"] = []
+            m["breadth_use_case"] = None
             continue
-        if st not in cache:
+        uc = usecase_for(st)
+        m["breadth_use_case"] = uc
+        key = (uc, st)
+        if key not in cache:
             try:
-                res = svc.controls_for_use_case("network_security", sub_topic=st, limit=limit)
-                cache[st] = [
+                res = svc.controls_for_use_case(uc, sub_topic=st, limit=limit)
+                cache[key] = [
                     {"control_id": c.get("control_id"), "title": c.get("title"),
                      "source_regulation": c.get("source_regulation"), "severity": c.get("severity")}
                     for c in res.get("controls", [])
                 ]
             except Exception:
-                cache[st] = []
-        m["regulatory_breadth"] = cache[st]
+                cache[key] = []
+        m["regulatory_breadth"] = cache[key]