feat(llm): 任务 LLM 配置链改为任何状态都可修改

任务结束(done/failed/timeout)后主 Agent 对话仍走任务配置链,链上模型出问题时
既不能改配置链、也就没法继续交互。去掉 HTTP 与 DB 事务两处终态拦截,前端弹窗
对终态任务同样开放编辑与保存(顺带修掉 queued 状态也不能编辑的口子)。

终态任务保存时不再重开额度阻塞意图:那些意图会从 blocked 挪到 open,既没有
worker 执行、也不再满足「重跑意图」的可重跑条件,反而变成死状态。终态任务想
继续跑仍走重跑意图/新增目标,由它们把任务重新 admit 回运行态。

db/task_context.go

@@ -402,6 +402,8 @@ FROM task_llm_profiles WHERE task_id=$1 ORDER BY position`, taskID)
 // ReplaceTaskLLMProfiles atomically replaces and resets the explicit task chain.
 // activeProfileID=0 selects the first entry. An empty list restores the existing
 // agent-binding/global fallback behavior.
+// 终态(done/failed/timeout)任务同样允许改链:任务结束后主 Agent 对话仍会走这条链,
+// 链上模型不可用时必须能换,否则已完成任务就再也没法交互了。
 func (d *DB) ReplaceTaskLLMProfiles(taskID int64, profileIDs []int64, activeProfileID int64) error {
 	tx, err := d.Begin()
 	if err != nil {
@@ -411,16 +413,13 @@ func (d *DB) ReplaceTaskLLMProfiles(taskID int64, profileIDs []int64, activeProf
 	// Keep the task -> profile lock order shared by all task LLM mutations and
 	// DeleteProfile. Inserts below may take KEY SHARE locks on llm_profiles for
 	// their foreign keys, so the task row must be locked before any of them.
-	var status string
-	if err := tx.QueryRow(`SELECT status FROM tasks WHERE id=$1 AND deleted_at IS NULL FOR UPDATE`, taskID).Scan(&status); err != nil {
+	var lockedID int64
+	if err := tx.QueryRow(`SELECT id FROM tasks WHERE id=$1 AND deleted_at IS NULL FOR UPDATE`, taskID).Scan(&lockedID); err != nil {
 		if err == sql.ErrNoRows {
 			return fmt.Errorf("task %d not found", taskID)
 		}
 		return err
 	}
-	if IsTerminal(status) {
-		return fmt.Errorf("terminal task cannot change LLM profiles")
-	}
 	if _, err := tx.Exec(`DELETE FROM task_llm_profiles WHERE task_id=$1`, taskID); err != nil {
 		return err
 	}