【后端接口】称号合成：低阶称号合成高阶的配方链

local TITLE_CHAIN = { bronze = 1, silver = 2, gold = 3, platinum = 4, diamond = 5 }
function TitleCompose.compose(actor, lowRank)
    local highRank = lowRank + 1
    local need = 3
    local owned = 0
    for _, tid in ipairs(actor.ownedTitles) do
        if TITLE_RANK[tid] == lowRank then owned = owned + 1 end
    end
    if owned < need then return false, "低阶称号不足 " .. need .. " 个" end
    -- 扣除三个低阶称号
    local removed = 0
    for i, tid in ipairs(actor.ownedTitles) do
        if removed < need and TITLE_RANK[tid] == lowRank then
            table.remove(actor.ownedTitles, i)
            removed = removed + 1
        end
    end
    Title.grant(actor, highRank)
    return true
end

function TitleCompose.inheritBest(actor, lowRank, highRank)
    local bestAtk = 0
    for _, tid in ipairs(actor.ownedTitles) do
        if TITLE_RANK[tid] == lowRank then
            bestAtk = math.max(bestAtk, TITLE_DEF[tid].atk)
        end
    end
    TITLE_DEF[highRank].atk = math.max(TITLE_DEF[highRank].atk, bestAtk * 3)
end