fix(tss-party): increase stdin buffer to 1MB for large TSS messages

Default 64KB buffer was truncating large TSS protocol messages in round 3+

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/settings.local.json

@@ -479,7 +479,11 @@
       "Bash(./node_modules/.bin/tsc:*)",
       "Bash(npm ls:*)",
       "Bash(npm run build:win:*)",
-      "Bash(npm run clean:*)"
+      "Bash(npm run clean:*)",
+      "Bash(git cherry-pick:*)",
+      "Bash(git stash:*)",
+      "Bash(docker compose build:*)",
+      "Bash(git log:*)"
     ],
     "deny": [],
     "ask": []

backend/mpc-system/services/service-party-app/tss-party/main.go

@@ -223,6 +223,8 @@ func executeKeygen(
 	go func() {
 		defer inWg.Done()
 		scanner := bufio.NewScanner(os.Stdin)
+		// 增加 buffer 大小到 1MB，默认 64KB 可能不够大消息
+		scanner.Buffer(make([]byte, 1024*1024), 1024*1024)
 		for scanner.Scan() {
 			select {
 			case <-ctx.Done():