Belt link leftover loop never executes — unfitted items not compacted

[ILLISIS]

Bug

In module/edge/belt_link.lua, the push_belt_link function attempts to compact leftover items back to the front of item_stacks when not all items fit in the chest. However the loop bounds are inverted, so the loop never runs and the caller cannot determine what remains.

Code

-- belt_link.lua:111-114
if item_stacks_count > space then
    for index = 1, space - item_stacks_count do  -- e.g. space=3, count=5 → range 1,-2 → never runs
        item_stacks[index] = item_stacks[index + space]
    end

Why it's wrong

• space = slots available in the chest (items successfully placed)
• item_stacks_count = total items to place
• When item_stacks_count > space, space - item_stacks_count is negative
• In Lua, for i = 1, -2 never executes (positive step, limit less than start)
• The leftover items at item_stacks[space+1 .. item_stacks_count] are never shifted to the front
• item_stacks is left with nil holes at the front and stale data at the back — the caller cannot tell what remains

Fix

Swap the operands and clear the trailing slots after the shift:

if item_stacks_count > space then
    for index = 1, item_stacks_count - space do
        item_stacks[index] = item_stacks[index + space]
    end
    for index = item_stacks_count - space + 1, item_stacks_count do
        item_stacks[index] = nil
    end

Impact

Items that don't fit in the destination chest are silently lost rather than being returned to the source for retry on the next tick.