Add a mock workflow script and load the example plugin

Why: Mock mode needs a path that drives the real step runner, and the example plugin should fail the host test if its workflow or slot question is wrong.
Evidence: go test ./internal/plugins/ -run TestRepoExamplePluginLoads passed. The brief intent asks 主题是什么？ and keeps the topic slot.
Impact: #workflow is only the mock runner. The example plugin itself is in the Dev repo.
Refs: feature/agent-harness-p4
Co-authored-by: Cursor <cursoragent@cursor.com>

internal/plugins/host_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"agent-system-backend/internal/intentgate"
@@ -208,3 +209,46 @@ func TestWorkflowScriptCannotEscape(t *testing.T) {
 		t.Fatal("script path outside the plugin dir should be rejected")
 	}
 }
+
+func TestRepoExamplePluginLoads(t *testing.T) {
+	root := filepath.Join("..", "..", "..", "plugins")
+	if _, err := os.Stat(filepath.Join(root, "example", "workflows", "demo-brief.json")); err != nil {
+		t.Skip("example plugin is not beside this module")
+	}
+	dir := t.TempDir()
+	st, err := store.OpenSQLite(filepath.Join(dir, "test.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	regTools := tools.NewRegistry()
+	regTools.RegisterBuiltin()
+	host := New(st, regTools, settings.NewService(st), root)
+	gate := intentgate.New()
+	wf := workflow.NewRegistry()
+	host.OnIntents = func(overlay []json.RawMessage) error {
+		return gate.Rebuild(context.Background(), overlay)
+	}
+	host.OnWorkflows = func(defs []core.WorkflowDef, scripts map[string]string) error {
+		wf.Set(defs, scripts)
+		return nil
+	}
+	if err := host.LoadDir()["example"]; err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := wf.ByIntent("demo.brief"); !ok {
+		t.Fatal("demo.brief is not bound")
+	}
+	body, ok := wf.Script("demo.script", "workflows/scripts/demo.py")
+	if !ok || !strings.Contains(body, `wf.tool("time_now"`) {
+		t.Fatalf("script %q", body)
+	}
+	got := gate.Recognize(context.Background(), "写一份简报")
+	if got.ID != "demo.brief" || len(got.Missing) != 1 || got.Missing[0].Question != "主题是什么？" {
+		t.Fatalf("%+v", got)
+	}
+	filled := gate.Recognize(context.Background(), "主题：核能 写一份简报")
+	if filled.Slots["topic"] != "核能" || len(filled.Missing) != 0 {
+		t.Fatalf("%+v", filled)
+	}
+}

internal/runtime/mock.go

@@ -7,6 +7,7 @@ import (
 
 	"agent-system-backend/internal/docgen"
 	"agent-system-backend/internal/squadadapter"
+	"agent-system-backend/internal/workflow"
 	core "agent-system-core"
 )
 
@@ -212,6 +213,17 @@ func (m *MockRunner) Execute(rc RunCtx) error {
 			addText("Agent-Squad 编排完成：" + summary + "。步骤与子代理见右栏「计划」「代理」。")
 		}
 
+	case strings.Contains(user, "#workflow"):
+		res, err := (WorkflowRunner{}).run(rc, workflow.Launch{Def: mockWorkflow()})
+		if err != nil {
+			if res.Summary != "" {
+				addText(res.Summary)
+			}
+			addText("演示工作流没有跑完：" + err.Error())
+			break
+		}
+		parts = append(parts, res.Parts...)
+
 	case strings.Contains(user, "#error"):
 		return fmt.Errorf("mock: 演示失败路径（#error 指令）")
 
@@ -229,7 +241,7 @@ func (m *MockRunner) Execute(rc RunCtx) error {
 			core.Part{Type: core.PartToolResult, Process: true, ToolResult: &core.ToolResultPart{CallID: callID, Status: res.Status, Summary: truncateForJSON(res.Output, 120)}},
 		)
 		rc.Emit(core.EvRunPhase, core.RunPhasePayload{Phase: core.PhaseResponding})
-		reply := fmt.Sprintf("（mock 回复）你说：%s\n\n这是 mock runner 的脚本化回复——未调用真实模型。可发送 #hitl / #agents / #doc / #error 触发对应演示路径。", user)
+		reply := fmt.Sprintf("（mock 回复）你说：%s\n\n这是 mock runner 的脚本化回复——未调用真实模型。可发送 #hitl / #agents / #doc / #workflow / #error 触发对应演示路径。", user)
 		idx := 0
 		for _, r := range reply {
 			rc.Emit(core.EvMessageDelta, core.MessageDeltaPayload{Index: idx, Text: string(r)})
@@ -257,6 +269,23 @@ func (m *MockSubagent) Execute(rc RunCtx) error {
 	return nil
 }
 
+func mockWorkflow() core.WorkflowDef {
+	return core.WorkflowDef{
+		ID: "mock.workflow", Title: "演示工作流",
+		Steps: []core.WorkflowStep{
+			{ID: "length", Title: "篇幅", Kind: "hitl", Hitl: &core.HITLCardTemplate{
+				Question: "要多长？", Kind: core.HITLKindChoice, AllowFreeInput: false,
+				Choices: []core.HITLChoice{
+					{ID: "short", Label: "短", Description: "一段", Impact: "只写一段"},
+					{ID: "long", Label: "长", Description: "几段", Impact: "会写得更长"},
+				},
+			}},
+			{ID: "save", Title: "成稿", Kind: "artifact", Artifact: "mock-brief.md", Prompt: "篇幅：{{steps.length.output}}\n{{input}}"},
+			{ID: "note", Title: "收件", Kind: "card", Card: &core.ActivityCardTemplate{Kind: core.CardKindResult, Title: "演示工作流完成"}},
+		},
+	}
+}
+
 func truncateForJSON(s string, n int) string {
 	r := []rune(s)
 	if len(r) <= n {