feat(controller): 工具仓库、Skills 录入、多轮追问与终端运行日志

- 插件/MCP 改为通用工具仓库：内置、HTTP MCP、本机命令（stdio）三类工具，可增删改、
  按 Agent 分配；定义变更自动提升下发版本并重发，删除即回收分配并通知 Agent 清空。
- 旧 desktop-filesystem 降级为仓库中的一个内置条目；本机预设工具改为总控只展示、
  Agent 默认启用，任务执行来源新增 builtin（审计 task.builtin_tool_execution）。
- Skills 补齐录入闭环：新建或按名称覆盖更新，并可从旧版技能目录（SKILL.md + skill.json）
  批量导入；同名更新保持标识不变并自动重新应用，旧包入口脚本只提示不执行。
- 单独指派支持基于某条已完成任务的多轮追问：任务内容框仍下发无上下文的一次性任务，
  追问时由总控组装历史（仅成功轮次、默认最近 50 轮 / 约 6 万字符），会话按 Agent 隔离；
  执行动态把同一会话合并为一条记录，任务详情弹窗底部提供继续对话输入框。
- 任务详情支持运行中观测：打开期间每 2 秒刷新，终端风格输出全部事件并自动滚动；
  progress 事件不改变任务状态且顺延无进展超时，避免正在执行工具的任务被误判超时。
- 修复 build.ps1 缺 UTF-8 BOM 导致 build.bat 在 PowerShell 5.1 下语法报错。

controller/internal/controlplane/skills.go

@@ -11,6 +11,10 @@ import (
 	"time"
 )
 
+// maxSkillContentBytes bounds one Skill Markdown document. The Agent applies the
+// same limit so content is never silently truncated after deployment.
+const maxSkillContentBytes = 50000
+
 // Skill is a safe Markdown-only capability guide owned by the controller.
 type Skill struct {
 	ID        string `json:"id"`
@@ -85,25 +89,64 @@ func (c *ControlPlane) SkillDocument(skillID string) (SkillDocument, error) {
 	return document, nil
 }
 
+// SaveSkill stores one Markdown-only Skill package. A skill is identified by its
+// display name, so importing an updated version keeps the identity — and therefore
+// every existing Agent assignment — intact instead of creating a duplicate.
 func (c *ControlPlane) SaveSkill(input SkillInput) (Skill, error) {
 	name, version, content := strings.TrimSpace(input.Name), strings.TrimSpace(input.Version), strings.TrimSpace(input.Content)
 	if name == "" || version == "" || content == "" {
 		return Skill{}, errors.New("请完整填写 Skill 名称、版本和内容")
 	}
-	if len([]rune(name)) > 80 || len([]rune(version)) > 40 || len(content) > 50000 {
+	if len([]rune(name)) > 80 || len([]rune(version)) > 40 || len(content) > maxSkillContentBytes {
 		return Skill{}, errors.New("Skill 内容或名称过长")
 	}
-	id, err := randomHex(16)
-	if err != nil {
-		return Skill{}, err
-	}
 	sum := sha256.Sum256([]byte(content))
+	checksum := hex.EncodeToString(sum[:])
 	now := time.Now().UTC().Format(time.RFC3339Nano)
-	if _, err = c.db.Exec("INSERT INTO skill_packages(skill_id, name, version, content, checksum, updated_at) VALUES (?, ?, ?, ?, ?, ?)", id, name, version, content, hex.EncodeToString(sum[:]), now); err != nil {
-		return Skill{}, fmt.Errorf("无法保存 Skill: %w", err)
+	skillID := ""
+	err := c.db.QueryRow("SELECT skill_id FROM skill_packages WHERE name = ?", name).Scan(&skillID)
+	switch {
+	case errors.Is(err, sql.ErrNoRows):
+		skillID, err = randomHex(16)
+		if err != nil {
+			return Skill{}, err
+		}
+		if _, err = c.db.Exec("INSERT INTO skill_packages(skill_id, name, version, content, checksum, updated_at) VALUES (?, ?, ?, ?, ?, ?)", skillID, name, version, content, checksum, now); err != nil {
+			return Skill{}, fmt.Errorf("无法保存 Skill: %w", err)
+		}
+		c.recordAudit("skill.package_saved", "controller", "skill:"+skillID, "completed", "已保存经哈希校验的 Skill 包。")
+	case err != nil:
+		return Skill{}, fmt.Errorf("无法读取 Skill: %w", err)
+	default:
+		if _, err = c.db.Exec("UPDATE skill_packages SET version = ?, content = ?, checksum = ?, updated_at = ? WHERE skill_id = ?", version, content, checksum, now, skillID); err != nil {
+			return Skill{}, fmt.Errorf("无法保存 Skill: %w", err)
+		}
+		c.recordAudit("skill.package_updated", "controller", "skill:"+skillID, "completed", "已按名称覆盖更新 Skill 包内容与版本。")
+	}
+	c.redeploySkill(skillID)
+	return Skill{ID: skillID, Name: name, Version: version, Checksum: checksum, UpdatedAt: now}, nil
+}
+
+// redeploySkill re-sends an updated Skill to the Agents that already selected it.
+func (c *ControlPlane) redeploySkill(skillID string) {
+	rows, err := c.db.Query("SELECT agent_id FROM agent_skill_assignments WHERE skill_id = ?", skillID)
+	if err != nil {
+		return
+	}
+	agentIDs := make([]string, 0)
+	for rows.Next() {
+		var agentID string
+		if rows.Scan(&agentID) == nil {
+			agentIDs = append(agentIDs, agentID)
+		}
+	}
+	rows.Close()
+	for _, agentID := range agentIDs {
+		if _, err := c.db.Exec("UPDATE agent_skill_assignments SET apply_status = 'pending', last_error = '', updated_at = ? WHERE agent_id = ? AND skill_id = ?", time.Now().UTC().Format(time.RFC3339Nano), agentID, skillID); err != nil {
+			continue
+		}
+		go c.pushSkills(agentID)
 	}
-	c.recordAudit("skill.package_saved", "controller", "skill:"+id, "completed", "已保存经哈希校验的 Skill 包。")
-	return Skill{ID: id, Name: name, Version: version, Checksum: hex.EncodeToString(sum[:]), UpdatedAt: now}, nil
 }
 
 func (c *ControlPlane) DeploySkill(skillID string, agentIDs []string) error {