Test that a visitor can't pick up the island owner's drop

docs/test-audit.md

@@ -54,7 +54,10 @@ After the refactor, the bot suite's 82 checks all passed on Paper 26.2 (2026-11-
 
 ### Gaps
 
-- **A visitor picking up an item that isn't theirs.** Pickup has its own rules (your own throws and death drops are allowed), so the break check doesn't cover it. A bot check was tried on 2026-11-10: items summoned at a visitor's feet on another island never appeared, and the suite keeps only the last server's console, so the cause wasn't found. Not covered yet. Next try: the island owner's bot drops an item next to the visitor, with a control for the visitor's own throw. Later finding (2026-11-10): nothing in Voidwell removes an item entity except the void, so the emerald most likely fell off the island's edge; it isn't data loss.
+- **A visitor picking up an item that isn't theirs:** covered on 2026-11-11 by `travelAndTeams` on 26.2 (19/19).
+  - The owner drops a golden apple, which is moved to the visiting kid's feet on a temporary barrier floor. It stays there, and the visitor doesn't get it.
+  - Control: the visitor's own drop, moved the same way, comes back to them.
+  - What made the earlier tries look wrong: the island is one block wide, so drops fell into the void, and the owner standing at the bell picked their own apple back up. The owner is a spectator during this check, so they can't pick anything up.
 
 - **Anything with a player on Paper 26.3.** ViaVersion clients are disconnected there when they move. Checked again on 2026-11-10: the newest ViaVersion and ViaBackwards builds on Modrinth are the ones already in use, and the bot library has no native 26.3 support. Server-only checks run there. This waits for a newer bot client or a real one (T21).
 - **A real client:** how the bell, meter and labels look and feel (T21).

test/suite.mjs

@@ -495,6 +495,40 @@ const tests = {
     let pos = await where('Ash')
     check('travel: visiting Birch\'s island', Math.hypot(pos.x - bPos.x, pos.z - bPos.z) < 20, JSON.stringify(pos))
     await heard(b, /Ash.*is visiting your island/, 4000).then(() => check('travel: the owner is told', true)).catch(e => check('travel: the owner is told', false, e.message))
+    // Look, don't take. The owner drops an apple at the visitor's feet and steps away: the visitor mustn't pick it up.
+    // Control: an apple the visitor drops themselves comes back to them.
+    const goldApples = () => count(a, 'golden_apple')
+    const before0 = goldApples()
+    // A OneBlock island is one block wide, so a drop would fall into the void: a barrier floor for this check only.
+    const fp = await where('Ash'), fx = Math.floor(fp.x), fz = Math.floor(fp.z), fy = Math.floor(fp.y) - 1
+    await s.run(`execute in minecraft:oneblock run fill ${fx - 3} ${fy} ${fz - 3} ${fx + 3} ${fy} ${fz + 3} barrier keep`, /filled|No blocks/i)
+    await s.run('give Birch golden_apple 1', /Gave/)
+    await s.run('execute in minecraft:oneblock run tp Birch Ash', /Teleported/)
+    await sleep(800)
+    await b.look(0, -Math.PI / 2, true)
+    await b.toss(b.registry.itemsByName.golden_apple.id, null, 1)
+    // The bell is close by: as a spectator the owner can't take their own apple back while the visitor stands on it.
+    await s.run('gamemode spectator Birch', /Set|game mode/i)
+    await s.run(`execute in minecraft:oneblock run tp Birch ${birchBell.x + 0.5} ${birchBell.y} ${birchBell.z + 2.5}`, /Teleported/)
+    await sleep(1500)
+    // A throw lands a block or two away; put the apple right at the visitor's feet, within pickup reach.
+    await s.run(`execute in minecraft:oneblock as @e[type=item,x=${fx},y=${fy},z=${fz},distance=..6] run tp @s Ash`, /Teleported/)
+    await sleep(4000)
+    const ap = await where('Ash')
+    const lying = await s.run(`execute in minecraft:oneblock positioned ${ap.x} ${ap.y} ${ap.z} if entity @e[type=item,distance=..3]`, /Test (passed|failed)/)
+    check('travel: a visitor can\'t pick up what the owner dropped', goldApples() === before0 && /passed/.test(lying), `Ash apples ${before0} -> ${goldApples()}, item still there: ${/passed/.test(lying)}`)
+    await s.run('gamemode survival Birch', /Set|game mode/i)
+    await s.run('give Ash golden_apple 1', /Gave/)
+    await sleep(800)
+    const mine = goldApples()
+    await a.look(0, -Math.PI / 2, true)
+    await a.toss(a.registry.itemsByName.golden_apple.id, null, 1)
+    await sleep(1500)
+    await s.run(`execute in minecraft:oneblock as @e[type=item,x=${fx},y=${fy},z=${fz},distance=..6] run tp @s Ash`, /Teleported/)
+    await sleep(4000)
+    check('travel: control: a visitor picks their own drop back up', goldApples() === mine, `Ash apples ${mine} -> after toss and wait ${goldApples()}`)
+    await s.run(`execute in minecraft:oneblock run kill @e[type=item,x=${fx},y=${fy},z=${fz},distance=..6]`, /Killed|No entity/i)
+    await s.run(`execute in minecraft:oneblock run fill ${fx - 3} ${fy} ${fz - 3} ${fx + 3} ${fy} ${fz + 3} air replace barrier`, /filled|No blocks/i)
     // Look, don't touch.
     const target = a.blockAt(new (await import('vec3')).Vec3(Math.floor(bPos.x), 100, Math.floor(bPos.z)))
     const kind = target?.name