test(simulation): lock standalone-HQ-as-ordinary-settlement-row invariant (T-1074)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/atlas/city_context_reader.rs

@@ -1154,6 +1154,50 @@ mod tests {
         );
     }
 
+    // ─── D-242 corp-HQ settlement model (T-1074/T-1075) ──────────────────────
+    //
+    // A Standalone-HQ settlement (economy_import/corporations.py:
+    // populate_standalone_hq_settlements) is inserted into atlas_city_names as
+    // an ORDINARY row — same schema, same fields, no corp linkage marker (the
+    // corp<->settlement relationship lives on corporations.headquarters_body,
+    // not on atlas_city_names). This module's test fixture schema
+    // (make_settlements_db, above) never had a corp_id column to begin with —
+    // this test makes that design invariant explicit: read_body_settlements
+    // (the D-211 placement pipeline's input) cannot distinguish a
+    // corp-Standalone-HQ row from a wiki-pooled city, by construction. If a
+    // future change ever needs to special-case corp-originated settlements,
+    // it will have to be threaded through explicitly — this test fails the
+    // moment that stops being true silently.
+
+    #[test]
+    fn read_body_settlements_treats_standalone_hq_row_identically_to_pooled_city() {
+        // "Gate Corporation" here stands in for a Phase-B-inserted
+        // Standalone-HQ row (name = corp proper_name, economic_role from
+        // corp_hq_placement.toml's standalone_economic_role, population from
+        // the T-1075 Zipf bake, settlement_class from the same bake/override
+        // path as any other city) — indistinguishable in shape from the
+        // ordinary pooled cities "Tributarium"/"Ruhr" it sits alongside.
+        let db = make_settlements_db(&[
+            ("Tributarium", "manufacturing", 2_727_273_224, Some("PopulationBudget")),
+            ("Ruhr", "manufacturing", 1_363_636_611, Some("PopulationBudget")),
+            ("Gate Corporation", "manufacturing", 909_090_165, Some("NameLocked")),
+        ]);
+        let reader = CityContextReader::open(&db).expect("open");
+        let cities = reader.read_body_settlements("PlanetX").expect("read");
+        assert_eq!(cities.len(), 3, "all three rows read back, HQ or not");
+
+        let hq = cities
+            .iter()
+            .find(|c| c.name == "Gate Corporation")
+            .expect("Standalone-HQ row must be present");
+        // Every CityRecord field the D-211 pipeline reads is populated exactly
+        // like an ordinary city's — nothing marks this row as corp-originated.
+        assert_eq!(hq.economic_role, "manufacturing");
+        assert_eq!(hq.population, 909_090_165);
+        assert_eq!(hq.settlement_class, SettlementClass::NameLocked);
+        assert!(!hq.is_capital, "Standalone HQ is not a capital by default");
+    }
+
     // ─── read_body_city_names (T-949) ────────────────────────────────────────
 
     #[test]