feat(plugins): 服务路径/适配器名冲突进裁决而非崩溃或硬拒绝（用户要求 A+B）

此前两类冲突各有问题：
A) 两个插件声明同一条 /api/plugins/http/ 服务路径 → 分发器按加载顺序静默
   选一个（装个新插件就可能改变既有路径归属）。
B) 插件装与内置/他插件同名的适配器 → 硬错误 ErrAdapterNameReserved / owned by。

用户要求：都改成「报冲突、列出候选、运维选一个保留、选择持久化」，绝不崩溃
或拒绝启动。

## A 类：插件 HTTP 服务路径冲突
- dispatch（plugin_http_routes.go）同路径多认领时不再 load-order 选边：未裁决
  返回 409 并点名候选；已裁决按赢家分发。
- route_conflicts.go：RouteConflicts/RouteWinner/ResolveRouteConflict，只统计
  loaded 且未禁用的插件；赢家插件若不再声明该路径，裁决作废回未裁决态。

## B 类：适配器名冲突
- InstallAdapter 撞名（内置或他插件所有）不再硬拒，改挂起：现任继续服务，候选
  入 AdapterConflicts，返回 typed ErrAdapterConflictPending（区分「代码错」）。
- ResolveAdapterConflict：incumbent 保留现任 / candidate 真正装上插件版（绕过
  reserved 门禁——这是运维显式授权覆盖内置的唯一入口）并转移归属。
- 现任内置永不被静默覆盖，守住「第三方插件不得篡改内核发行物」信任边界。

## 持久化 + WebAPI + WebUI
- 两张裁决表落 .route-conflicts.json（routes + adapters），LoadDir 时读回；
  重启后插件再装同名适配器自动套用上次裁决。
- WebAPI：GET /api/plugins/conflicts 列冲突；POST {kind,path|name,winner} 裁决。
- WebUI：插件页顶部「冲突裁决」卡片，逐条列路径/适配器冲突 + 候选 + 裁决按钮。

## 测试
- 单测 conflict_arbitration_test.go 6 项全过：路径冲突检测/裁决/持久化/重启、
  赢家消失回退、适配器撞名挂起/incumbent/candidate/归属转移、非法 winner 拒绝、
  自身更新不受影响（token 轮换不走冲突路径）。
- e2e conflict_arbitration_e2e_test.go 2 项全过（真二进制）：两插件抢路径→409
  点名→裁决→200 赢家应答→/v1/models 无回归；插件装 shadow openai→挂起→现任
  保留→裁决 candidate→插件版生效→冲突清空。
- 全量 build + vet 通过，既有 lua/gateway/core 回归无破坏。

修正过程中发现并修了一个真 bug：LoadAdapterSource 对 key≠declared 的适配器
重装会建第二个池、留旧池继续服务（v2 装了 v1 还在跑）——改成统一按注册键
归档，裁决 candidate 后新版本才真正生效。

internal/lua/plugins.go

@@ -292,6 +292,23 @@ type Plugins struct {
 	// is state and not a convention).
 	adapterOwn     *adapterOwnership
 	adapterOwnOnce sync.Once
+	// routeWinners records the operator's arbitration for contested HTTP service
+	// paths: a path two+ plugins declared, resolved to one winning plugin. Keyed
+	// by normalized path. See route_conflicts.go — a contested path that is NOT
+	// in here is unresolved and the dispatcher returns 409 rather than silently
+	// picking a load-order winner. Persisted in .route-conflicts.json.
+	routeWinners map[string]string
+	// adapterWinners records the operator's arbitration for an adapter NAME two
+	// things claimed (user requirement B): "incumbent" keeps the built-in / first
+	// plugin, "candidate:<plugin>" lets that plugin's version win. Persisted in
+	// .route-conflicts.json beside routeWinners. See route_conflicts.go.
+	adapterWinners map[string]string
+	// adapterConflicts holds adapter-name installs currently SUSPENDED pending an
+	// operator decision: a plugin tried to install an adapter whose name an
+	// incumbent already holds. The incumbent keeps serving; the candidate waits
+	// here (with its code) until arbitrated. In-memory only — a restart replays
+	// the install, which re-suspends unless a persisted winner says otherwise.
+	adapterConflicts map[string]*AdapterConflict
 	// shards runs exported functions on private VMs so blocking work can be
 	// genuinely parallel. See plugin_shard.go for why the shared VM's lock makes
 	// concurrency impossible and what a shard must therefore never touch.
@@ -583,6 +600,12 @@ func (ps *Plugins) LoadDir() error {
 	if err := ps.LoadKernelPermissions(); err != nil {
 		log.Printf("[core] plugin kernel permissions not loaded: %v", err)
 	}
+	// Route-conflict arbitrations are operator policy too: who wins a service
+	// path two plugins both declared. Must be in place before the first request
+	// is dispatched, or a contested path would 409 until the operator re-chose.
+	if err := ps.LoadRouteConflicts(); err != nil {
+		log.Printf("[core] plugin route conflicts not loaded: %v", err)
+	}
 	if _, err := os.Stat(ps.dir); os.IsNotExist(err) {
 		return nil
 	}