Add TUI kanban board, review workflow, and new task statuses

Replace task statuses (pending/running/succeeded/failed/cancelled) with
a kanban workflow: todo → in_progress → in_review → done/wontdo.

When a non-review agent task completes, the API auto-creates a child
review task and moves the parent to in_review. Only humans can move
tasks from in_review to done/wontdo via the TUI.

New components:
- cmd/tui: bubbletea kanban board with $EDITOR integration
- POST /api/v1/tasks/{id}/complete: agent completion callback
- Operator --api-url flag for completion callbacks
- ProviderQueue sets tasks to in_progress on pickup
- AgentTask reconciler calls /complete on job finish

internal/database/tasks.go

@@ -2,6 +2,7 @@ package database
 
 import (
 	"context"
+	"fmt"
 	"strconv"
 	"time"
 
@@ -24,7 +25,7 @@ func (db *DB) CreateTask(ctx context.Context, req models.CreateTaskRequest) (*mo
 		ExtraTools:   req.ExtraTools,
 		ParentTaskID: req.ParentTaskID,
 		PoolRef:      req.PoolRef,
-		Status:       models.StatusPending,
+		Status:       models.StatusTodo,
 	}
 	if task.ExtraTools == nil {
 		task.ExtraTools = []string{}
@@ -79,7 +80,7 @@ func (db *DB) GetTask(ctx context.Context, id string) (*models.Task, error) {
 }
 
 func (db *DB) ListPendingTasks(ctx context.Context) ([]models.Task, error) {
-	return db.listTasksByStatus(ctx, string(models.StatusPending))
+	return db.listTasksByStatus(ctx, string(models.StatusTodo))
 }
 
 func (db *DB) listTasksByStatus(ctx context.Context, status string) ([]models.Task, error) {
@@ -130,13 +131,13 @@ func (db *DB) ListTasks(ctx context.Context, status string, repository string) (
 }
 
 func (db *DB) UpdateTaskStatus(ctx context.Context, id string, req models.UpdateTaskRequest) error {
-	if req.Status == models.StatusRunning {
+	if req.Status == models.StatusInProgress {
 		_, err := db.Pool.Exec(ctx, `
 			UPDATE tasks SET status = $2, job_name = COALESCE(NULLIF($3, ''), job_name), started_at = NOW()
 			WHERE id = $1`, id, req.Status, req.JobName)
 		return err
 	}
-	if req.Status == models.StatusSucceeded || req.Status == models.StatusFailed {
+	if req.Status == models.StatusDone || req.Status == models.StatusWontdo {
 		_, err := db.Pool.Exec(ctx, `
 			UPDATE tasks SET status = $2, result = COALESCE(NULLIF($3, ''), result),
 				error_message = COALESCE(NULLIF($4, ''), error_message), completed_at = NOW()
@@ -147,6 +148,70 @@ func (db *DB) UpdateTaskStatus(ctx context.Context, id string, req models.Update
 	return err
 }
 
+func (db *DB) CompleteTask(ctx context.Context, id string, req models.CompleteTaskRequest) (*models.Task, error) {
+	task, err := db.GetTask(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	if req.ErrorMessage != "" {
+		_, err := db.Pool.Exec(ctx, `
+			UPDATE tasks SET status = 'todo', error_message = $2, completed_at = NOW()
+			WHERE id = $1`, id, req.ErrorMessage)
+		if err != nil {
+			return nil, err
+		}
+		task.Status = models.StatusTodo
+		task.ErrorMessage = req.ErrorMessage
+		return task, nil
+	}
+
+	if req.Result != "" {
+		_, err := db.Pool.Exec(ctx, `
+			UPDATE tasks SET result = $2 WHERE id = $1`, id, req.Result)
+		if err != nil {
+			return nil, err
+		}
+		task.Result = req.Result
+	}
+
+	if task.Command != "review" {
+		_, err := db.Pool.Exec(ctx, `
+			UPDATE tasks SET status = 'in_review', completed_at = NOW()
+			WHERE id = $1`, id)
+		if err != nil {
+			return nil, err
+		}
+		task.Status = models.StatusInReview
+
+		reviewTask := models.CreateTaskRequest{
+			Command:      "review",
+			Repository:   task.Repository,
+			Ref:          task.Ref,
+			IssueNumber:  task.IssueNumber,
+			PRNumber:     task.PRNumber,
+			Body:         task.Body,
+			Author:       task.Author,
+			ParentTaskID: task.ID,
+			PoolRef:      task.PoolRef,
+		}
+		if _, err := db.CreateTask(ctx, reviewTask); err != nil {
+			return nil, fmt.Errorf("create review task: %w", err)
+		}
+
+		return task, nil
+	}
+
+	_, err = db.Pool.Exec(ctx, `
+		UPDATE tasks SET status = 'in_review', completed_at = NOW()
+		WHERE id = $1`, id)
+	if err != nil {
+		return nil, err
+	}
+	task.Status = models.StatusInReview
+	return task, nil
+}
+
 func scanTasks(rows pgx.Rows) ([]models.Task, error) {
 	var tasks []models.Task
 	for rows.Next() {