test(trade): seed one stack per deposit so every transfer is a pick-up and place

[u9g]

Rebased on master. The first commit is the test half of #3983 (trades = 2): with master's 11 uses, one stack per deposit would need 44 stacks, more than the inventory holds. If #3983 merges first this rebases down to the second commit.

Problem

trade seeds two 64-stacks of emeralds. bot.transfer takes the first stack of the item it finds, so each deposit picks up 64, right-clicks the price in one at a time and puts the rest back — 36 right clicks per deposit for the wooden sword trade. Every click is a server tick, so pre-1.14 the test spends ~5s in 101 clicks.

Changes

Seed one stack of exactly the price for each deposit, in the order the trades consume them ([p0, p0, 2, 2, 1, 1, 36, 36] emeralds and [1, 1] books). transfer then finds the exact stack first and every deposit is pick-up + place. Assertions are unchanged; they only check totals.

The slots are set with Promise.all (as clearInventory already does): on 1.21.3+ (noAckOnCreateSetSlotPacket) there is no ack for set_creative_slot, so each setInventorySlot waits 400ms for a rejection; serialised over 10 slots that is 4s.

Verification

trade on the base branch vs this PR (clicks are window_clicks from the packet trace):

Version	Clicks	Before	After
1.8.8	101 → 34	6976ms	3577ms
1.9.4	101 → 34	7075ms	3625ms
1.13.2	101 → 34	7037ms	3232ms
1.16.5	—	—	2348ms
1.21.8	29 → 21	2909ms	2073ms
26.1	29 → 21	3497ms	2618ms

On 1.14+ the server moves whole stacks into the trade slots itself when a trade is selected, so the click count barely changes there; the gain is from the concurrent slot setup. The remaining ~1s of the pre-1.14 runs is the two command-block sleeps (#4029).

[github-actions]

Tests more than 1.5x slower than master (durations are noisy, so this is informational):

   3513ms ->   11076ms  mineflayer_external 1.10.2v nether
   3411ms ->   10486ms  mineflayer_external 1.11.2v nether
   3438ms ->    9826ms  mineflayer_external 1.8.8v nether
   3459ms ->   12114ms  mineflayer_external 1.9.4v nether
   1440ms ->    7176ms  mineflayer_external 1.16.5v activateItem
  12915ms ->   20360ms  mineflayer_external 1.17.1v nether
  12936ms ->   24698ms  mineflayer_external 1.19v nether
   4955ms ->   14772ms  mineflayer_external 1.21.3v nether
   9601ms ->   15542ms  mineflayer_external 1.21.4v nether
   8689ms ->   13726ms  mineflayer_external 1.21.6v nether

[rom1504]

Approved, resolved conflict and merge