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/tui/taskformat.go

@@ -0,0 +1,134 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+
+	"git.unkin.net/unkin/forgebot/pkg/models"
+)
+
+type editableTask struct {
+	Status       string `yaml:"status"`
+	Message      string `yaml:"message"`
+	ErrorMessage string `yaml:"error_message"`
+}
+
+type newTask struct {
+	Command    string `yaml:"command"`
+	Repository string `yaml:"repository"`
+	Ref        string `yaml:"ref"`
+	Body       string `yaml:"body"`
+	Author     string `yaml:"author"`
+	Skill      string `yaml:"skill"`
+	PoolRef    string `yaml:"pool_ref"`
+}
+
+func marshalTaskForEdit(task *models.Task) []byte {
+	var b strings.Builder
+	fmt.Fprintf(&b, "# forgebot task %s\n", task.ID)
+	b.WriteString("# Editable: status, message, error_message\n\n")
+
+	et := editableTask{
+		Status:       string(task.Status),
+		Message:      task.Result,
+		ErrorMessage: task.ErrorMessage,
+	}
+	data, _ := yaml.Marshal(et)
+	b.Write(data)
+
+	b.WriteString("\n# -- Context (read-only) --\n")
+	fmt.Fprintf(&b, "# command: %s\n", task.Command)
+	fmt.Fprintf(&b, "# repository: %s\n", task.Repository)
+	fmt.Fprintf(&b, "# ref: %s\n", task.Ref)
+	fmt.Fprintf(&b, "# author: %s\n", task.Author)
+	if task.IssueNumber > 0 {
+		fmt.Fprintf(&b, "# issue: %d\n", task.IssueNumber)
+	}
+	if task.PRNumber > 0 {
+		fmt.Fprintf(&b, "# pr: %d\n", task.PRNumber)
+	}
+	fmt.Fprintf(&b, "# created: %s\n", task.CreatedAt.Format("2006-01-02T15:04:05Z"))
+	if task.Body != "" {
+		b.WriteString("#\n# body:\n")
+		for _, line := range strings.Split(task.Body, "\n") {
+			fmt.Fprintf(&b, "#   %s\n", line)
+		}
+	}
+	if task.Result != "" {
+		b.WriteString("#\n# result:\n")
+		for _, line := range strings.Split(task.Result, "\n") {
+			fmt.Fprintf(&b, "#   %s\n", line)
+		}
+	}
+
+	return []byte(b.String())
+}
+
+func unmarshalEditedTask(data []byte) (*editableTask, error) {
+	var et editableTask
+	if err := yaml.Unmarshal(data, &et); err != nil {
+		return nil, fmt.Errorf("parse edited task: %w", err)
+	}
+	return &et, nil
+}
+
+func diffEditableTask(original *models.Task, edited *editableTask) *models.UpdateTaskRequest {
+	req := &models.UpdateTaskRequest{}
+	changed := false
+
+	if edited.Status != string(original.Status) {
+		req.Status = models.TaskStatus(edited.Status)
+		changed = true
+	}
+	if edited.Message != original.Result {
+		req.Message = edited.Message
+		changed = true
+	}
+	if edited.ErrorMessage != original.ErrorMessage {
+		req.ErrorMessage = edited.ErrorMessage
+		changed = true
+	}
+
+	if !changed {
+		return nil
+	}
+	return req
+}
+
+func marshalNewTask() []byte {
+	var b strings.Builder
+	b.WriteString("# New forgebot task\n\n")
+	nt := newTask{
+		Command:    "implement",
+		Repository: "",
+		Ref:        "main",
+		Body:       "",
+		Author:     "",
+		Skill:      "",
+		PoolRef:    "",
+	}
+	data, _ := yaml.Marshal(nt)
+	b.Write(data)
+	return []byte(b.String())
+}
+
+func unmarshalNewTask(data []byte) (*models.CreateTaskRequest, error) {
+	var nt newTask
+	if err := yaml.Unmarshal(data, &nt); err != nil {
+		return nil, fmt.Errorf("parse new task: %w", err)
+	}
+	if nt.Command == "" || nt.Repository == "" {
+		return nil, fmt.Errorf("command and repository are required")
+	}
+	return &models.CreateTaskRequest{
+		Command:    nt.Command,
+		Repository: nt.Repository,
+		Ref:        nt.Ref,
+		Body:       nt.Body,
+		Author:     nt.Author,
+		Skill:      nt.Skill,
+		PoolRef:    nt.PoolRef,
+	}, nil
+}