refactor: pluginize text cleaning and tool NoMemory control

- SDK: ToolDef.NoMemory field, PluginSDK.RegisterTextCleaner/TextCleaners
- Registry: aggregate text cleaners from plugins, expose CleanText()
- Memory: replace hardcoded QQ regex CleanTemplateText with dynamic CleanText/SetTextCleaner
- StageHost: add ToolDef(name) lookup
- eventloop: check ToolDef.NoMemory before emitMemoryCandidate
- context/Prune: replace hardcoded agentcli/terminal source filter with ToolsUsed NoMemory check
- agentcli/cmd: mark tools with NoMemory: true
- main.go: wire memory.SetTextCleaner(pluginReg.CleanText)

internal/plugins/cmd/plugin.go

@@ -110,6 +110,7 @@ func (p *Plugin) Start(s *sdk.PluginSDK) error {
 	s.RegisterTool("cmd_run", sdk.ToolDef{
 		Name:        "cmd_run",
 		Description: "执行一条系统命令并返回输出。适用于查询系统信息、运行脚本、操作文件等单次命令场景。命令在临时 shell 中执行，不支持交互。如需交互式终端（如 vim、ssh、top），请使用 terminal_create 相关工具。",
+		NoMemory:    true,
 		Parameters: map[string]interface{}{
 			"type": "object",
 			"properties": map[string]interface{}{