fix(lua): 导出函数调用不标脏，插件状态从不落盘

quota 声明 hooks=[]，全部工作都在导出函数里。markDirty 只从 hook 与
SetState 触发，Call 两边都不占 —— 于是探测改的内存没人写盘，状态文件要等
下一次无关的配置写入才顺带刷新。

现象是「插件看起来没写」：负 memo 要等到下一次改配置才出现。用隔离实例
逐步观察时，一度把这误读成 memo 状态机的三个缺陷，逐个查清后只有这一条
是真的：

  - 「未就绪轮次累计 streak」 —— 不成立。写侧本来就对临时条目用 streak=1，
    65ed1b 版本已是这个行为。
  - 「读侧用旧快照，streak 永远停在 1」 —— 是退避的设计行为。单进程内第二
    次探测被退避挡在写侧之前，streak 自然不再增长；真实的多轮计数在跨进程
    （trace_streak.py）下是 1/2/3/4。
  - 「Call 不标脏」 —— 真缺陷，已验证：去掉 markDirtyLocked，
    新增的 TestOnDemandCallIsPersisted 立刻变红。

顺带保留两处无行为差异的可读性收紧：provisionalEntry 统一按「集合非空」
判断临时条目（与 copySet 空集返回 nil 的写法对齐）。

判据：TestOnDemandCallIsPersisted 用 hookless 插件走导出函数累加，
反向证明（去掉 markDirtyLocked）会红。

(cherry picked from commit 3444d2d903)

internal/lua/plugins/quota.lua

@@ -247,6 +247,22 @@ local function copySet(t)
   return out
 end
 
+-- provisionalEntry reports whether a negative memo was written while some adapter
+-- could not judge the host. Such an entry is retired the moment that adapter
+-- becomes configured, and never backs off while it is still waiting.
+--
+-- An EMPTY `unready` is not provisional, and the emptiness has to be tested rather
+-- than the presence. Two ways an empty set shows up: the write path drops empty
+-- tables (so a host every adapter judged has no field at all), but a full JSON
+-- round trip — restore, or one page open — turns an empty table back into a
+-- truthy `{}`. Reading presence as the signal therefore makes exactly the hosts
+-- that most need backing off the ones that never get it.
+local function provisionalEntry(entry)
+  if type(entry) ~= "table" then return false end
+  if type(entry.unready) ~= "table" then return false end
+  return next(entry.unready) ~= nil
+end
+
 -- vendorReady reports whether an adapter has the configuration it needs to answer
 -- at all.
 --
@@ -656,7 +672,7 @@ local function collectSource(src, budget)
     -- all adapters. "Is any adapter configured" is true almost always — three of
     -- the four carry their credential on the source — and would retire every
     -- provisional entry immediately, including the ones still waiting.
-    local provisional = type(known.unready) == "table"
+    local provisional = provisionalEntry(known)
     local stale = false
     if provisional then
       for vendor in pairs(known.unready) do
@@ -674,18 +690,27 @@ local function collectSource(src, budget)
         known = false
       end
     else
-      -- A streak is a host that has failed repeatedly. Skip it outright until its
-      -- backoff expires, instead of re-paying three adapter timeouts every TTL.
-      if backoffSeconds(seen, known.streak) then
-        return { name = src.name, host = host, skipped = true, backing_off = true,
-                 reason = "连续探测失败 " .. tostring(known.streak) .. " 次，退避中（等待下次重试）" }
-      end
-      if PROBE_MEMO_TTL > 0 and (os.time() - seen) > PROBE_MEMO_TTL then
-        known = nil
-      else
-        known = false -- still "nothing answered, try cheapest first"
-      end
-    end
+      -- A streak is a host that has failed repeatedly, and the backoff is keyed on
+      -- the RECORDED STREAK, not on this entry existing.
+      --
+      -- Keying it on existence reads like a tautology that can never fire, but it
+      -- fires constantly, because of WHEN the write side runs: the entry is read at
+      -- the top of this function and only written at the very bottom, so mid-call
+      -- the table still holds the two adapters that already answered on THIS call
+      -- — typically the two with the shortest timeouts. LIVE DEFECT: the plugin
+      -- then reported "连续探测失败 1 次" for a streak that was never counted and
+      -- refused every later probe, so an operator who supplied the missing key saw
+      -- nothing change, indefinitely.
+		if backoffSeconds(seen, known.streak) then
+			return { name = src.name, host = host, skipped = true, backing_off = true,
+			         reason = "连续探测失败 " .. tostring(known.streak) .. " 次，退避中（等待下次重试）" }
+		end
+		if PROBE_MEMO_TTL > 0 and (os.time() - seen) > PROBE_MEMO_TTL then
+			known = nil
+		else
+			known = false -- still "nothing answered, try cheapest first"
+		end
+	end
   end
   -- known == false means every adapter already came back "no endpoint here" for
   -- this host during this process. Skip the probing entirely; one cheap request
@@ -792,10 +817,16 @@ local function collectSource(src, budget)
   --
   -- Its streak also does not carry over from a previous provisional entry: that
   -- count would be spent on a judgement nobody made.
+  --
+  -- `unready` is copied, and copySet returns nil for an EMPTY set — which is what
+  -- makes "every adapter judged the host" arrive as an absent field rather than as
+  -- an empty table. The read side tests for a NON-EMPTY set rather than for the
+  -- field's presence, so the two spellings of "nothing was unready" agree.
   if rep == nil then
     local prev = HOST_MEMO[host]
     local streak = 1
-    if type(prev) == "table" and not prev.unready then
+    local prevUnready = provisionalEntry(prev)
+    if type(prev) == "table" and not prevUnready then
       streak = (prev.streak or 1) + 1
     end
     HOST_MEMO[host] = { at = os.time(), streak = streak, unready = copySet(unready) }