refactor(civilization): pick best available land defender as city build default

- Replace hardcoded 'warriors' default with pickNextBuild() for both
  founded and captured cities
- Captured cities now adopt the new owner's tech level when selecting
  their default unit (e.g., Phalanx if Bronze Working is known)
- Add verification tests for tech-dependent defaults on founding and capture

src/games/civilization/CivilizationLogic.js

@@ -449,13 +449,14 @@ export function foundCity(rules, state, unit, name) {
     size: 1,
     foodBox: 0,
     shieldBox: 0,
-    build: { type: 'unit', id: 'warriors' },
+    build: { type: 'unit', id: 'warriors' }, // safe fallback; pickNextBuild overrides below
     buildings: {},
     worked: [],
     emphasis: 'balanced',
     routes: [],
     boughtThisTurn: false,
   };
+  pickNextBuild(rules, state, city); // best available land defender, not always warriors
   state.nextCityId += 1;
   if (civCities(state, unit.civ).length === 0) city.buildings.palace = true;
   // Civ II treats the city square as having a road (its main early trade).
@@ -1102,7 +1103,7 @@ export function captureCity(rules, state, unit, city) {
   city.size = Math.max(1, city.size - 1);
   city.routes = [];
   city.shieldBox = 0;
-  city.build = { type: 'unit', id: 'warriors' };
+  pickNextBuild(rules, state, city); // best available land defender for the new owner
   for (const u of state.units.filter((un) => un.homeCity === city.id)) u.homeCity = null;
   unit.x = city.x;
   unit.y = city.y;

tools/verifyCivilization.js

@@ -393,6 +393,30 @@ if (RULES) {
     check('capital named for leader', city.name === 'Civ0 City');
     check('min distance blocks adjacent city', !Logic.canFoundCity(RULES, st, 6, 5));
     check('distance 2 allowed', Logic.canFoundCity(RULES, st, 7, 5));
+    check('default build is the best available defender, not always warriors',
+      city.build.type === 'unit' && city.build.id === 'warriors');
+  }
+
+  // Founding/capturing picks the best available land defender, not a fixed
+  // 'warriors' default — a civ that already knows Bronze Working should
+  // found (and inherit captured cities) straight onto Phalanx.
+  {
+    const st = makeFlatState({ civs: 2 });
+    st.civs[0].known.bronzeworking = true;
+    const settler = Logic.spawnUnit(RULES, st, 0, 'settlers', 5, 5, null);
+    const city = Logic.foundCity(RULES, st, settler);
+    check('founded city with Bronze Working known defaults to Phalanx',
+      city.build.type === 'unit' && city.build.id === 'phalanx');
+
+    st.civs[1].known.bronzeworking = false;
+    const enemySettler = Logic.spawnUnit(RULES, st, 1, 'settlers', 9, 9, null);
+    const enemyCity = Logic.foundCity(RULES, st, enemySettler);
+    check('enemy without Bronze Working still defaults to Warriors',
+      enemyCity.build.type === 'unit' && enemyCity.build.id === 'warriors');
+    const attacker = Logic.spawnUnit(RULES, st, 0, 'legion', enemyCity.x, enemyCity.y, null);
+    Logic.captureCity(RULES, st, attacker, enemyCity);
+    check('captured city re-defaults using the new owner\'s tech (Phalanx)',
+      enemyCity.build.type === 'unit' && enemyCity.build.id === 'phalanx');
   }
 
   // Growth on flat grassland: foodbox fills, granary keeps half.