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/plugin_adapter_bridge.go

@@ -26,6 +26,7 @@ package lua
 import (
 	"fmt"
 	"sort"
+	"strings"
 	"sync"
 
 	golua "github.com/aarzilli/golua/lua"
@@ -103,35 +104,65 @@ func (ps *Plugins) InstallAdapter(plugin, name, code string) (string, error) {
 	if ps.vm == nil {
 		return "", fmt.Errorf("install_adapter: no adapter VM available")
 	}
-	// Rule 3 first: an adapter another plugin already owns is off-limits.
+	// A name conflict used to be a hard rejection (owned by another plugin, or
+	// shadows a built-in). The user now wants it SUSPENDED for operator
+	// arbitration instead of refused outright: the incumbent keeps serving, the
+	// candidate waits in the conflicts list, and the operator picks a winner in
+	// the WebUI. The install still returns a (typed) error so the caller knows it
+	// did not take effect — but it is ErrAdapterConflictPending, not a dead end.
+	incumbent := ""
 	if owner := ps.adapterOwner().ownedBy(name); owner != "" && owner != plugin {
-		return "", fmt.Errorf("install_adapter: adapter %q is owned by plugin %q and cannot be replaced by %q",
-			name, owner, plugin)
+		incumbent = "plugin:" + owner
+	} else if containsNameFold(ps.vm.bundledNames(), name) {
+		incumbent = "operator (built-in)"
 	}
-	// Rules 1+2 (path safety + no shadowing built-ins) live in
-	// InstallPluginAdapter so there is exactly one enforcement point.
+	if incumbent != "" {
+		if ps.recordAdapterConflict(name, incumbent, plugin, code) {
+			// The operator already chose THIS candidate in a prior session. Install
+			// for real via LoadAdapterSource, which bypasses the reserved-name gate
+			// — that explicit operator override is exactly what the arbitration is
+			// FOR, and re-suspending it on every restart would be a loop.
+			if err := ps.vm.LoadAdapterSource(name, code); err != nil {
+				return "", err
+			}
+			return ps.finishInstall(plugin, name), nil
+		}
+		return "", &ErrAdapterConflictPending{Name: name, Incumbent: incumbent}
+	}
+	// No conflict: normal install path. Rules 1+2 (path safety + no shadowing
+	// built-ins) live in InstallPluginAdapter so there is exactly one
+	// enforcement point. (The shadow check there is now unreachable for a
+	// genuine built-in — it is caught above and suspended — but kept as the
+	// single authority for path safety and any future reserved set.)
 	if err := ps.vm.InstallPluginAdapter(name, code); err != nil {
 		return "", err
 	}
-	// Ownership is recorded under the name sources will actually reference. A
-	// script may declare a name different from the registration key, and it is
-	// the declared name that ends up in the registry — recording it under the
-	// key would leave the adapter un-owned and therefore mutable by anyone.
-	// Ownership is recorded under the name sources will actually reference. A
-	// script may declare a name different from the registration key, and it is
-	// the declared name that ends up in the registry — recording it under the
-	// key would leave the adapter un-owned and therefore mutable by anyone.
-	//
-	// Both names are recorded: the registration key so a later update through
-	// the same key still matches, and the declared name so a lookup by the name
-	// a source references also matches. Both entries are cleared together on
-	// remove.
+	return ps.finishInstall(plugin, name), nil
+}
+
+// finishInstall records adapter ownership under BOTH the registration key and
+// the declared name (a script may declare a name different from the key, and it
+// is the declared name sources reference — recording only the key would leave
+// the adapter un-owned and therefore mutable by anyone). Both entries are
+// cleared together on remove.
+func (ps *Plugins) finishInstall(plugin, name string) string {
 	effective := ps.vm.EffectiveAdapterName(name)
 	ps.adapterOwner().set(effective, plugin)
 	if effective != name {
 		ps.adapterOwner().set(name, plugin)
 	}
-	return effective, nil
+	return effective
+}
+
+// containsNameFold reports whether name is in names (case-insensitive, matching
+// ValidateAdapterName's reserved-name comparison).
+func containsNameFold(names []string, name string) bool {
+	for _, n := range names {
+		if strings.EqualFold(n, name) {
+			return true
+		}
+	}
+	return false
 }
 
 // UpdateAdapter replaces an adapter a plugin previously installed — the token