feat(web): 任务详情页新增探索链路播报板

按创建时间分页平铺展示探索节点,作为探索链路图的时间轴视图,
复用同一份 exploration_nodes 数据,不影响链路图。

- 后端 NodesPage/NodesByIDs/EdgesTouching:分页下推 SQL,
  支持 kind/state 过滤、payload/origin 搜索、正倒序,
  并补出当页节点的相邻边与对端节点
- 新增 GET /api/exploration/nodes(仅本任务节点,不含继承)
- 播报板:时间轴分行、按天分组、类型快筛、搜索防抖、
  自动刷新、直播位未读提示、展开看上下游与 payload
- 补 mock,NEXT_PUBLIC_MOCK=1 下可无后端预览

db/exploration.go

@@ -785,6 +785,129 @@ func (s *ExplorationStore) Nodes(limit int) ([]*Node, error) {
 	return scanNodes(rows)
 }
 
+// NodeFilter narrows a NodesPage query. Empty fields include every value.
+type NodeFilter struct {
+	Kinds  []string // exploration_nodes.kind
+	States []string // exploration_nodes.state
+	Query  string   // case-insensitive substring over payload text / origin
+	Asc    bool     // true = oldest first (replay); default newest first (broadcast)
+}
+
+// NodesPage returns one 1-based page of this exploration's nodes plus the total
+// matching count. The 播报板 reads the graph as a time series, so it pages in SQL
+// rather than pulling the whole graph like Nodes does. Ordering is by id, which
+// is BIGSERIAL and therefore creation order — stable when several nodes share a
+// created_at second.
+func (s *ExplorationStore) NodesPage(f NodeFilter, page, size int) ([]*Node, int, error) {
+	if page < 1 {
+		page = 1
+	}
+	if size <= 0 {
+		size = 20
+	}
+	if size > 200 {
+		size = 200
+	}
+	offset := (page - 1) * size
+
+	conds := []string{"exploration_id=$1"}
+	args := []any{s.expID}
+	addIn := func(column string, values []string) {
+		if len(values) == 0 {
+			return
+		}
+		marks := make([]string, 0, len(values))
+		for _, v := range values {
+			args = append(args, v)
+			marks = append(marks, "$"+fmt.Sprint(len(args)))
+		}
+		conds = append(conds, column+" IN ("+strings.Join(marks, ",")+")")
+	}
+	addIn("kind", f.Kinds)
+	addIn("state", f.States)
+	if q := strings.TrimSpace(f.Query); q != "" {
+		args = append(args, "%"+q+"%")
+		mark := "$" + fmt.Sprint(len(args))
+		conds = append(conds, "(payload::text ILIKE "+mark+" OR COALESCE(origin,'') ILIKE "+mark+")")
+	}
+	where := " WHERE " + strings.Join(conds, " AND ")
+
+	var total int
+	if err := s.db.QueryRow(`SELECT COUNT(*) FROM exploration_nodes`+where, args...).Scan(&total); err != nil {
+		return nil, 0, err
+	}
+	order := "DESC"
+	if f.Asc {
+		order = "ASC"
+	}
+	args = append(args, size, offset)
+	rows, err := s.db.Query(`SELECT `+nodeCols+` FROM exploration_nodes`+where+
+		` ORDER BY id `+order+
+		` LIMIT $`+fmt.Sprint(len(args)-1)+` OFFSET $`+fmt.Sprint(len(args)), args...)
+	if err != nil {
+		return nil, 0, err
+	}
+	defer rows.Close()
+	nodes, err := scanNodes(rows)
+	if err != nil {
+		return nil, 0, err
+	}
+	return nodes, total, nil
+}
+
+// NodesByIDs loads the given nodes of this exploration in id order. Used to
+// resolve the neighbours of a 播报板 page without fetching the whole graph.
+func (s *ExplorationStore) NodesByIDs(ids []int64) ([]*Node, error) {
+	if len(ids) == 0 {
+		return nil, nil
+	}
+	args := make([]any, 0, len(ids)+1)
+	args = append(args, s.expID)
+	marks := make([]string, 0, len(ids))
+	for _, id := range ids {
+		args = append(args, id)
+		marks = append(marks, "$"+fmt.Sprint(len(args)))
+	}
+	rows, err := s.db.Query(`SELECT `+nodeCols+` FROM exploration_nodes
+WHERE exploration_id=$1 AND id IN (`+strings.Join(marks, ",")+`) ORDER BY id`, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	return scanNodes(rows)
+}
+
+// EdgesTouching returns every edge with one end among ids — the 播报板 uses it to
+// spell out where a node came from and what it produced.
+func (s *ExplorationStore) EdgesTouching(ids []int64) ([]Edge, error) {
+	if len(ids) == 0 {
+		return nil, nil
+	}
+	args := make([]any, 0, len(ids)+1)
+	args = append(args, s.expID)
+	marks := make([]string, 0, len(ids))
+	for _, id := range ids {
+		args = append(args, id)
+		marks = append(marks, "$"+fmt.Sprint(len(args)))
+	}
+	list := strings.Join(marks, ",")
+	rows, err := s.db.Query(`SELECT src_id, rel, dst_id FROM exploration_edges
+WHERE exploration_id=$1 AND (src_id IN (`+list+`) OR dst_id IN (`+list+`))`, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Edge
+	for rows.Next() {
+		var e Edge
+		if err := rows.Scan(&e.From, &e.Rel, &e.To); err != nil {
+			return nil, err
+		}
+		out = append(out, e)
+	}
+	return out, rows.Err()
+}
+
 // Edge is one row from exploration_edges.
 type Edge struct {
 	From int64