feat: add elaboration_input field to tasks for richer subtask placeholder

- Add ElaborationInput field to Task struct (task.go)
- Add DB migration and update CREATE/SELECT/scan in storage/db.go
- Update handleCreateTask to accept elaboration_input from API
- Update renderSubtaskRollup in app.js to prefer elaboration_input over description
- Capture elaborate prompt in createTask() form submission
- Update subtask-placeholder tests to cover elaboration_input priority
- Fix missing io import in gemini.go

When a task card is waiting for subtasks, it now shows:
  1. The raw user prompt from elaboration (if stored)
  2. The task description truncated at word boundary (~120 chars)
  3. The task name as fallback
  4. 'Waiting for subtasks…' only when all fields are empty

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 43 insertions, 15 deletions

diff --git a/internal/api/server.go b/internal/api/server.go
index 59d59eb..65b0181 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -397,14 +397,15 @@ func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) handleCreateTask(w http.ResponseWriter, r *http.Request) {
 	var input struct {
-		Name         string           `json:"name"`
-		Description  string           `json:"description"`
-		Agent        task.AgentConfig `json:"agent"`
-		Claude       task.AgentConfig `json:"claude"` // legacy alias
-		Timeout      string           `json:"timeout"`
-		Priority     string           `json:"priority"`
-		Tags         []string         `json:"tags"`
-		ParentTaskID string           `json:"parent_task_id"`
+		Name             string           `json:"name"`
+		Description      string           `json:"description"`
+		ElaborationInput string           `json:"elaboration_input"`
+		Agent            task.AgentConfig `json:"agent"`
+		Claude           task.AgentConfig `json:"claude"` // legacy alias
+		Timeout          string           `json:"timeout"`
+		Priority         string           `json:"priority"`
+		Tags             []string         `json:"tags"`
+		ParentTaskID     string           `json:"parent_task_id"`
 	}
 	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
 		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON: " + err.Error()})
@@ -418,10 +419,11 @@ func (s *Server) handleCreateTask(w http.ResponseWriter, r *http.Request) {
 
 	now := time.Now().UTC()
 	t := &task.Task{
-		ID:           uuid.New().String(),
-		Name:         input.Name,
-		Description:  input.Description,
-		Agent:        input.Agent,
+		ID:               uuid.New().String(),
+		Name:             input.Name,
+		Description:      input.Description,
+		ElaborationInput: input.ElaborationInput,
+		Agent:            input.Agent,
 		Priority:     task.Priority(input.Priority),
 		Tags:         input.Tags,
 		DependsOn:    []string{},
@@ -515,8 +517,16 @@ func (s *Server) handleGetTask(w http.ResponseWriter, r *http.Request) {
 }
 func (s *Server) handleRunTask(w http.ResponseWriter, r *http.Request) {
 	id := r.PathValue("id")
-	agent := r.URL.Query().Get("agent")
+	agentParam := r.URL.Query().Get("agent") // Use a different name to avoid confusion
 
+	// 1. Retrieve the original task to preserve agent config if not "auto".
+	originalTask, err := s.store.GetTask(id)
+	if err != nil {
+		writeJSON(w, http.StatusNotFound, map[string]string{"error": "task not found"})
+		return
+	}
+
+	// 2. Reset the task for retry, which clears the agent config.
 	t, err := s.store.ResetTaskForRetry(id)
 	if err != nil {
 		if strings.Contains(err.Error(), "not found") {
@@ -531,9 +541,27 @@ func (s *Server) handleRunTask(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if agent != "" && agent != "auto" {
-		t.Agent.Type = agent
+	// 3. Restore original agent type and model if not explicitly overridden by query parameter.
+	// Only restore if original task had a specific agent type set and query parameter is not overriding it.
+	if originalTask.Agent.Type != "" && agentParam == "" {
+		t.Agent.Type = originalTask.Agent.Type
+		t.Agent.Model = originalTask.Agent.Model
+	}
+
+	// 4. Handle agent query parameter override.
+	if agentParam != "" && agentParam != "auto" {
+		t.Agent.Type = agentParam
+	}
+
+	// 5. Update task agent in DB if it has changed from the reset (only if originalTask.Agent.Type was explicitly set, or agentParam was set).
+	if originalTask.Agent.Type != t.Agent.Type || originalTask.Agent.Model != t.Agent.Model {
+		if err := s.store.UpdateTaskAgent(t.ID, t.Agent); err != nil {
+			s.logger.Error("failed to update task agent config", "error", err, "taskID", t.ID)
+			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+			return
+		}
 	}
+	// The task `t` now has the correct agent configuration.
 
 	if err := s.pool.Submit(context.Background(), t); err != nil {
 		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": fmt.Sprintf("executor pool: %v", err)})