feat(lua): 适配器导入路径冲突校验（R6）——防静默覆盖与路径逃逸

用户要求：导入适配器时必须检查路径冲突，避免静默错误。

之前 UploadAdapter(name, code) 直接拼 adapter_dir/<name>.lua：
- name 含 "../" 或绝对路径会写到目录外
- name 与内置同名会静默覆盖，加载失败只报 "adapter X missing"，
  现场与病因分离

实现（internal/lua/adapter_validate.go）：
- ValidateAdapterName：字符集 ^[a-zA-Z0-9_-]+$，拒绝 /、\、..、绝对路径、空白
- ValidateAdapterPath：文件必须在 adapter_dir 内
- VM.InstallPluginAdapter：插件装内置名 → ErrAdapterNameReserved 拒
- Core.UploadAdapter：在 WriteFile 之前校验（防路径逃逸）
- Core.RemoveAdapter：也校验名字（防 os.Remove 越界）

设计取舍：保留名禁止只对插件生效，不对运维生效。
- operator 放 openai.lua 覆盖内置 = 文档化的热覆盖机制，放行
- 第三方插件静默换掉内核自带的协议翻译 = 篡改发行物，拒绝
- 先误做成了全拒，Start() 加载内置适配器直接崩，测试抓住后改对
  （TestLoadBundledAdapters 等锁住回归）

测试 12 个：路径穿越/绝对路径/保留段/空白/内置覆盖(允许 vs 插件拒绝)/
目录外加载/错误点名/热重载不回归。

验证：go test -tags luajit ./... 全绿。

internal/core/core.go

@@ -8,10 +8,10 @@ import (
 	"encoding/hex"
 	"fmt"
 	"log"
+	"net/url"
 	"os"
 	"path/filepath"
 	"sort"
-	"net/url"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -874,6 +874,14 @@ func (c *Core) UploadAdapter(name, code string) error {
 	if name == "" {
 		return fmt.Errorf("adapter name required")
 	}
+	// Validate name SAFETY before touching the filesystem (R6). A path-traversal
+	// name ("../openai") must be rejected BEFORE WriteFile, or it would already
+	// have escaped the adapter dir by the time LoadAdapter re-checks. Built-in
+	// names are allowed here: an admin uploading openai.lua is the documented
+	// override, same as placing the file in adapter_dir by hand.
+	if err := lua.ValidateAdapterName(name, nil); err != nil {
+		return err
+	}
 	if err := os.MkdirAll(c.cfg.AdapterDir, 0755); err != nil {
 		return err
 	}
@@ -885,6 +893,13 @@ func (c *Core) UploadAdapter(name, code string) error {
 }
 
 func (c *Core) RemoveAdapter(name string) error {
+	// Validate the name so a traversal name cannot os.Remove a file outside the
+	// adapter dir. A reserved (built-in) name is a legitimate delete target in
+	// the running VM, so reserved-name rejection is NOT applied here — only the
+	// path-safety character set is.
+	if err := lua.ValidateAdapterName(name, nil); err != nil {
+		return err
+	}
 	path := filepath.Join(c.cfg.AdapterDir, name+".lua")
 	_ = os.Remove(path)
 	c.vm.RemoveAdapter(name)