fix(rust): a zone resource carries its deadline as until (W1)

Stage 4 of docs/modules/rust/PLAN_LAST_FIXES.md, the module's half of W1.
A placed zone now reports `until`, reckoned from the answer as now plus
holdMs, so it lands a round trip after the game's own deadline and never
before it. Core's reconcile then files a zone gone past that deadline as
expired, where a reconnect used to log resource.orphaned five seconds
before the game's world.expired arrived. Crates and NPCs send no
holdMs, so they carry no until.

No core pin change: `until` has been in the resource contract all along,
and a core without the reconcile half only shows it on the console.

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

server/test/world.test.js

@@ -178,10 +178,13 @@ test('a zone crosses with its key, its duration, and the monument without the se
     server: 'main',
     body: { runId: '7', key: 'k1', monument: 'airfield_1', offsetX: 0, offsetZ: -20, radius: 40, holdMs: 5400000, name: 'Brawl' },
   })
-  // The ref carries the server: revert and reconcile are handed no params.
-  assert.deepStrictEqual(result.resources, [
-    { kind: 'world', ref: 'main:rg-7-1-1', payload: { serverId: 'main', what: 'zone', name: 'Z' } },
-  ])
+  // The ref carries the server: revert and reconcile are handed no params. The
+  // zone's deadline rides as `until` (W1); zones.test.js checks its value.
+  const [resource] = result.resources
+  assert.strictEqual(typeof resource.until, 'string')
+  const { until, ...rest } = resource
+  assert.deepStrictEqual(rest, { kind: 'world', ref: 'main:rg-7-1-1', payload: { serverId: 'main', what: 'zone', name: 'Z' } })
+  assert.strictEqual(result.resources.length, 1)
 })
 
 test('one resource per thing placed, and a repeated key is said to be one', async (t) => {