fix(P3): root-cause suppression — an empty-name GA no longer cascades

Council #2: the empty GA 2/5/2 spawned missing_status + policy_taxonomy_outlier +
a lighting classification on top of its real defect. An empty name means the
classifier can't be trusted, so detect_missing_status and check_policy now skip
blank-name GAs; the single root cause is empty_name (check_naming). Demo 2/5/2:
3 findings -> 1. tests/test_root_cause.py; full suite green (10 tests).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -61,6 +61,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **Root-cause suppression (external-review noise).** A GA with an **empty name** has an unreliable
+  classification, so it no longer cascades into a `missing_status_address` warning and a
+  `policy_taxonomy_outlier` — the single root cause (`empty_name` from `check_naming`) is kept and the
+  dependent findings are suppressed. On the demo house the empty `2/5/2` now yields one finding instead
+  of three. `tests/test_root_cause.py`.
+
 - **Noise & unsafe repairs surfaced by an external expert review on the demo house.** (1) Scene-control
   GAs (DPT 17/18) are no longer flagged as `missing_status` — they recall a preset and have no single
   state to read back (now `scene_no_status`, INFO), and `suggest_repairs` no longer synthesises a bogus

nickol_knx_mcp/analyze.py

@@ -249,6 +249,8 @@ def detect_missing_status(project: LoadedProject) -> list[dict[str, Any]]:
             continue
         if ga.intent != INTENT_FUNCTIONAL:
             continue  # reserve / logic / scratch GAs need no status by design
+        if not (ga.name or "").strip():
+            continue  # root cause is empty_name (check_naming); classification unreliable
         if ga.kind != "command":
             continue
         if ga.dpt_main is None:

nickol_knx_mcp/policy.py

@@ -131,6 +131,8 @@ def check_policy(project: LoadedProject, policy: dict[str, Any]) -> dict[str, An
         if ga.intent != INTENT_FUNCTIONAL or ga.main is None:
             continue
         seen_mains.add(ga.main)
+        if not (ga.name or "").strip():
+            continue  # empty name -> unreliable classification; root cause is empty_name
 
         # 1. main-group taxonomy conformance (only when the domain is known)
         allowed = mg.get(ga.main)

tests/test_root_cause.py

@@ -0,0 +1,53 @@
+"""Root-cause suppression (external-review noise): a GA with an empty name has an
+unreliable classification, so it must NOT cascade into missing_status and policy
+taxonomy findings — the single root cause is `empty_name` (check_naming).
+"""
+from nickol_knx_mcp.project import build_loaded_from_raw
+from nickol_knx_mcp.analyze import validate_naming, detect_missing_status
+from nickol_knx_mcp.policy import check_policy, load_policy
+
+
+def _ga(addr, name, dmain, dsub):
+    return {"name": name, "identifier": f"GA-{addr}", "raw_address": 0, "address": addr,
+            "project_uid": None, "dpt": {"main": dmain, "sub": dsub}, "data_secure": False,
+            "communication_object_ids": [], "description": "", "comment": ""}
+
+
+def _proj(gas):
+    raw = {"info": {"group_address_style": "ThreeLevel", "schema_version": "21"},
+           "group_addresses": gas, "communication_objects": {}, "devices": {},
+           "functions": {}, "topology": {}, "group_ranges": {}}
+    return build_loaded_from_raw(raw, "t.knxproj")
+
+
+def main():
+    # main 2 is a clear shutter zone; an empty-name 5.001 command sits in it
+    gas = {
+        "2/0/1": _ga("2/0/1", "Blind A up/down", 1, 8),
+        "2/0/2": _ga("2/0/2", "Blind B up/down", 1, 8),
+        "2/0/3": _ga("2/0/3", "Blind C up/down", 1, 8),
+        "2/5/2": _ga("2/5/2", "", 5, 1),   # EMPTY name, 5.001 command
+    }
+    p = _proj(gas)
+
+    naming = {f["code"] for f in validate_naming(p) if "2/5/2" in str(f.get("address", ""))}
+    status = [f for f in detect_missing_status(p) if "2/5/2" in str(f.get("address", ""))]
+    policy = [f for f in check_policy(p, load_policy())["findings"]
+              if "2/5/2" in str(f.get("address", ""))]
+
+    assert "empty_name" in naming, naming                 # the single root cause is kept
+    assert status == [], f"empty-name GA must not cascade to missing_status: {status}"
+    assert policy == [], f"empty-name GA must not cascade to policy taxonomy: {policy}"
+
+    # sanity: a NAMED command in the same setup is still checked
+    gas["2/0/9"] = _ga("2/0/9", "Blind D up/down", 1, 8)
+    p2 = _proj(gas)
+    assert any(f["address"] == "2/0/9" for f in detect_missing_status(p2)), \
+        "named command must still be flagged for missing status"
+
+    print("test_root_cause: OK — empty-name GA yields only empty_name; no missing_status / "
+          "policy cascade; named GAs still checked.")
+
+
+if __name__ == "__main__":
+    main()