Restore natural mob spawning

- Restore cave spawning and correct floor placement across platforms.
- Enforce category population limits and clamp ambient spawn batches.
- Honor mob-spawning rules and entity-ticking chunk admission.
- Separate chunk saving from configurable distance-despawn retention.
- Add spawning regressions and Folia gameplay acceptance coverage.

adapters/bukkit/plugin/src/test/gameplay/natural-spawning.mjs

@@ -0,0 +1,41 @@
+export default {
+  name: 'iris-natural-spawning',
+  description: 'Observe category-limited Iris ambient frogs and cave zombies on Folia.',
+  async run(context) {
+    const wait = (predicate, label, timeoutMs = 30000) => context.waitUntil(predicate, { label, timeoutMs, intervalMs: 100 })
+    const command = async (operation, expected, timeoutMs = 30000) => {
+      const response = await context.command(`/irisspawnqa ${operation}`, /SPAWN_QA_[A-Z]+(?:\s|$)/, timeoutMs)
+      context.expect(response.includes(expected) && !response.includes('SPAWN_QA_FAILED'), response)
+      return response
+    }
+    const entities = name => Object.values(context.bot.entities).filter(entity => entity.name === name)
+    await context.step('prepare the synthetic Iris world and dark cave', async () => {
+      await command('setup', 'SPAWN_QA_SETUP world=iris:spawn_qa seed=78264193', 180000)
+      await wait(() => Math.abs(context.bot.entity.position.y - 67) < 1, 'Fixture world teleport')
+    })
+    await context.step('fill the passive category through real Iris ambient spawning', async () => {
+      await command('frogs', 'SPAWN_QA_FROGS frogs=16 persistent=true removable=true ambient=true', 60000)
+      await wait(() => entities('frog').length === 16, 'All sixteen ambient frogs became visible')
+      context.report.irisNaturalSpawning = { visibleFrogs: entities('frog').length }
+    })
+    await context.step('spawn an authored seven-zombie batch with capacity two despite existing frogs', async () => {
+      await command('zombies', 'SPAWN_QA_ZOMBIES frogs=16 zombies=2 firstBatch=2 ambient=true', 60000)
+      await command('cave', 'SPAWN_QA_VIEW y=-46')
+      await wait(() => Math.abs(context.bot.entity.position.y + 46) < 1, 'Underground fixture teleport')
+      await wait(() => context.bot.blockAt(context.bot.entity.position.clone().set(8, -47, 8))?.name === 'cave_air', 'Live cave_air block reached the client')
+      await wait(() => entities('zombie').length === 2, 'Both ambient cave zombies became visible')
+      context.expect(entities('zombie').every(entity => entity.position.y < -42), 'Zombies were not inside the underground chamber')
+      context.report.irisNaturalSpawning.visibleZombies = entities('zombie').length
+      context.report.irisNaturalSpawning.caveAir = true
+    })
+    await context.step('repeat fifty ambient attempts without exceeding the hostile capacity', async () => {
+      await command('stress', 'SPAWN_QA_STRESS attempts=50 zombies=2', 60000)
+      await command('check', 'SPAWN_QA_RESULT frogs=16 zombies=2 firstBatch=2 persistent=true removable=true caveAir=true light=0', 30000)
+      context.expect(entities('zombie').length === 2, 'Client observed a hostile capacity overflow')
+      context.report.irisNaturalSpawning.saturatedAttempts = 50
+      context.report.irisNaturalSpawning.firstHostileBatch = 2
+      context.report.irisNaturalSpawning.removeWhenFarAwayAllowed = true
+      context.report.irisNaturalSpawning.chunkSaving = true
+    })
+  }
+}