fix: LLM 工具循环 400、中断消息注入、ConPTY 终端支持

- agent: 工具轮请求尾部补 user 占位(zen 网关强制),tool 消息正确配对
- agent: 工具提醒/中断以 system 角色注入并带 [中断消息] 前缀,不进用户履历;系统提示词说明中断消息格式
- agentcli: 基于 ConPTY 的交互式终端(ptywin fork),terminal_create/read/write/resize/close/watch
- webui: server 输出通道适配器(保留 reasoning_content/disable_thinking)
- GUI: 沉浸式标题栏、icon 圆角重制、mascot 等打磨

internal/plugins/agentcli/pty_windows_test.go

@@ -0,0 +1,65 @@
+//go:build windows
+
+package agentcli
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+// TestNewCommandPtyConPTY 验证 Windows ConPTY 后端：一次性命令输出可读，
+// 交互式会话可写读往返。
+func TestNewCommandPtyConPTY(t *testing.T) {
+	ta, _, err := newCommandPty("cmd.exe /c echo conpty-ok", 24, 80)
+	if err != nil {
+		t.Fatalf("once: %v", err)
+	}
+	outA := drainFor(ta, 3*time.Second)
+	if !strings.Contains(string(outA), "conpty-ok") {
+		t.Fatalf("once output missing echo: %q", string(outA))
+	}
+	ta.Close()
+
+	tb, _, err := newCommandPty("cmd.exe", 24, 80)
+	if err != nil {
+		t.Fatalf("interactive: %v", err)
+	}
+	defer tb.Close()
+	time.Sleep(300 * time.Millisecond)
+	if _, err := tb.WriteString("echo hi-123\r\n"); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	outB := drainFor(tb, 3*time.Second)
+	if !strings.Contains(string(outB), "hi-123") {
+		t.Fatalf("interactive output missing echo: %q", string(outB))
+	}
+	if !tb.Running() {
+		t.Fatalf("interactive shell should still be running")
+	}
+}
+
+func drainFor(term ptyTerm, dur time.Duration) []byte {
+	deadline := time.Now().Add(dur)
+	buf := make([]byte, 4096)
+	var out []byte
+	for time.Now().Before(deadline) {
+		ch := make(chan struct{ N int; E error }, 1)
+		go func() {
+			n, e := term.Read(buf)
+			ch <- struct{ N int; E error }{n, e}
+		}()
+		select {
+		case r := <-ch:
+			if r.N > 0 {
+				out = append(out, buf[:r.N]...)
+			}
+			if r.E != nil {
+				return out
+			}
+		case <-time.After(500 * time.Millisecond):
+			return out
+		}
+	}
+	return out
+}