fix: 平台消息身份传递 — AI-Core 收到正确昵称而非永远 fallback 到管理员

- forwardToAICore 新增 nickname 字段，格式 "昵称 (QQ号)" 明确标识发送者
- 解决非管理员用户 @昔涟 时 AI 仍认为是管理员的身份污染问题
- 同时包含：管理员群聊插入抑制、markdown 粗体剥离、SearXNG 容器、ethend 窗口隐藏

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/platform-bridge/internal/adapter/qq/adapter.go

@@ -280,10 +280,7 @@ func (a *Adapter) ToUnified(rawMessage interface{}) (*bridge.UnifiedMessage, err
 func (a *Adapter) FromUnified(response *bridge.UnifiedResponse) ([]bridge.PlatformMessage, error) {
 	var msgs []bridge.PlatformMessage
 	for _, rm := range response.Messages {
-		content := rm.Content
-		if rm.FormatMode == "markdown" {
-			content = convertMarkdownToQQ(rm.Content)
-		}
+		content := convertMarkdownToQQ(rm.Content)
 		runes := []rune(content)
 		if len(runes) > 200 {
 			content = string(runes[:200])
@@ -421,6 +418,9 @@ func extractText(msg *OBv11Message) string {
 
 var cqImageRegex = regexp.MustCompile(`\[CQ:image,[^\]]*\]`)
 var cqURLRegex = regexp.MustCompile(`\burl=([^,\]]+)`)
+	var boldRegex = regexp.MustCompile(`\*\*(.+?)\*\*`)
+	var italicRegex = regexp.MustCompile(`\*(.+?)\*`)
+	var strikethroughRegex = regexp.MustCompile(`~~(.+?)~~`)
 
 // extractAttachments extracts image URLs from OBv11Message.
 // Handles both string format (CQ codes in raw_message) and array format (parsed segments).
@@ -473,8 +473,11 @@ func extractAttachments(msg *OBv11Message) []bridge.Attachment {
 	return attachments
 }
 
-// convertMarkdownToQQ converts common markdown to QQ-supported format.
+// convertMarkdownToQQ converts markdown to QQ plain-text format.
 func convertMarkdownToQQ(md string) string {
+	md = boldRegex.ReplaceAllString(md, "$1")
+	md = italicRegex.ReplaceAllString(md, "$1")
+	md = strikethroughRegex.ReplaceAllString(md, "$1")
 	md = removeHeadings(md)
 	md = removeCodeBlocks(md)
 	return md