feat(zones): a blank dome stack is 3 spheres, not 1 (runicnpc 9e, D326)

The org lead chose 3 by eye at noon in RunicNPC's 9d player session. The
zone step sends it when its stack is left blank, and the field's hint says
so. The wire is unchanged: the module always sends a stack, and the bridge's
own default for a dome without one stays 1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/eventWorld.js

@@ -60,6 +60,8 @@ const ZONE_MAX_RADIUS = 150
 const ZONE_MAX_MINUTES = 7 * 24 * 60
 const ZONE_MESSAGE_MAX = 256
 const DOME_STACK_MAX = 10
+/** A blank stack: 3 spheres, chosen by eye at noon in RunicNPC's 9d player session (D326). */
+const DOME_STACK_DEFAULT = 3
 
 /**
  * ZoneDomes' own sphere types, by the number its API takes (D194). Only Standard
@@ -725,7 +727,7 @@ const ACTIONS = [
         description:
           'A ZoneDomes dome over the zone. "standard" is a full shaded dome; the colours show only where the sphere meets the ground or a building. Needs ZoneDomes and RunicGatewayDomes.cs on the server. Blank is no dome.',
       },
-      { name: 'domeStack', type: 'int', required: false, example: 1, description: `How many spheres the dome stacks, 1 to ${DOME_STACK_MAX}; more is darker. Left blank, 1.` },
+      { name: 'domeStack', type: 'int', required: false, example: DOME_STACK_DEFAULT, description: `How many spheres the dome stacks, 1 to ${DOME_STACK_MAX}; more is darker. Left blank, ${DOME_STACK_DEFAULT}.` },
     ],
 
     async perform({ runId, idempotencyKey, params, verify }) {
@@ -777,7 +779,7 @@ const ACTIONS = [
         }
         const missing = domeMissing(mods)
         if (missing) return { ok: false, retry: false, error: missing }
-        dome = { type: kind.type, stack: stack === undefined ? 1 : stack }
+        dome = { type: kind.type, stack: stack === undefined ? DOME_STACK_DEFAULT : stack }
       }
 
       // The dry run stops here, and has checked everything it can without the