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
 	}

db/tasks_test.go

@@ -464,7 +464,7 @@ func TestTaskRelationsAndLLMFailoverChain(t *testing.T) {
 	}
 }
 
-func TestTaskContextRejectsDuplicatesAndTerminalEdits(t *testing.T) {
+func TestTaskContextRejectsDuplicatesAndAllowsTerminalLLMEdits(t *testing.T) {
 	d, err := Open(testDSN(t))
 	if err != nil {
 		t.Skipf("postgres unavailable (%v) - skipping", err)
@@ -480,6 +480,17 @@ func TestTaskContextRejectsDuplicatesAndTerminalEdits(t *testing.T) {
 		t.Fatal("duplicate source task ids should be rejected")
 	}
 
+	// 终态任务仍然可以改 LLM 配置链:任务结束后主 Agent 对话继续走这条链,
+	// 链上模型不可用时必须还能换。
+	profileID, err := d.SaveProfile(&LLMProfile{
+		Name: fmt.Sprintf("terminal-chain-%d", time.Now().UnixNano()), Format: "openai",
+		Model: "terminal-model", APIKey: "test-key",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = d.DeleteProfile(profileID) })
+
 	task, err := d.CreateTask("terminal", "goal", nil, 0, 0)
 	if err != nil {
 		t.Fatal(err)
@@ -488,8 +499,21 @@ func TestTaskContextRejectsDuplicatesAndTerminalEdits(t *testing.T) {
 	if err := d.SetStatus(task.ID, "done"); err != nil {
 		t.Fatal(err)
 	}
-	if err := d.ReplaceTaskLLMProfiles(task.ID, nil, 0); err == nil {
-		t.Fatal("terminal task LLM edit should be rejected")
+	if err := d.ReplaceTaskLLMProfiles(task.ID, []int64{profileID}, profileID); err != nil {
+		t.Fatalf("terminal task LLM edit should be allowed: %v", err)
+	}
+	got, err := d.GetTask(task.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fmt.Sprint(got.LLMProfileIDs) != fmt.Sprint([]int64{profileID}) {
+		t.Fatalf("terminal task chain not persisted: %v", got.LLMProfileIDs)
+	}
+	if got.ActiveLLMProfileID == nil || *got.ActiveLLMProfileID != profileID {
+		t.Fatalf("terminal task active profile not persisted: %v", got.ActiveLLMProfileID)
+	}
+	if err := d.ReplaceTaskLLMProfiles(task.ID, nil, 0); err != nil {
+		t.Fatalf("clearing a terminal task's chain should be allowed: %v", err)
 	}
 }