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/editor.go

@@ -0,0 +1,106 @@
+package tui
+
+import (
+	"context"
+	"os"
+	"os/exec"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"git.unkin.net/unkin/forgebot/pkg/models"
+)
+
+type editorFinishedMsg struct {
+	err error
+}
+
+func editTaskCmd(task *models.Task, client *Client) tea.Cmd {
+	data := marshalTaskForEdit(task)
+	tmpFile, err := os.CreateTemp("", "forgebot-task-*.yaml")
+	if err != nil {
+		return func() tea.Msg { return editorFinishedMsg{err: err} }
+	}
+	tmpPath := tmpFile.Name()
+	if _, err := tmpFile.Write(data); err != nil {
+		tmpFile.Close()
+		os.Remove(tmpPath)
+		return func() tea.Msg { return editorFinishedMsg{err: err} }
+	}
+	tmpFile.Close()
+
+	editor := resolveEditor()
+	c := exec.Command(editor, tmpPath)
+
+	return tea.ExecProcess(c, func(err error) tea.Msg {
+		defer os.Remove(tmpPath)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		edited, err := os.ReadFile(tmpPath)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		et, err := unmarshalEditedTask(edited)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		diff := diffEditableTask(task, et)
+		if diff == nil {
+			return editorFinishedMsg{}
+		}
+
+		err = client.UpdateTask(context.Background(), task.ID, *diff)
+		return editorFinishedMsg{err: err}
+	})
+}
+
+func newTaskEditorCmd(client *Client) tea.Cmd {
+	data := marshalNewTask()
+	tmpFile, err := os.CreateTemp("", "forgebot-new-*.yaml")
+	if err != nil {
+		return func() tea.Msg { return editorFinishedMsg{err: err} }
+	}
+	tmpPath := tmpFile.Name()
+	if _, err := tmpFile.Write(data); err != nil {
+		tmpFile.Close()
+		os.Remove(tmpPath)
+		return func() tea.Msg { return editorFinishedMsg{err: err} }
+	}
+	tmpFile.Close()
+
+	editor := resolveEditor()
+	c := exec.Command(editor, tmpPath)
+
+	return tea.ExecProcess(c, func(err error) tea.Msg {
+		defer os.Remove(tmpPath)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		edited, err := os.ReadFile(tmpPath)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		req, err := unmarshalNewTask(edited)
+		if err != nil {
+			return editorFinishedMsg{err: err}
+		}
+
+		_, err = client.CreateTask(context.Background(), *req)
+		return editorFinishedMsg{err: err}
+	})
+}
+
+func resolveEditor() string {
+	if e := os.Getenv("EDITOR"); e != "" {
+		return e
+	}
+	if e := os.Getenv("VISUAL"); e != "" {
+		return e
+	}
+	return "vi"
+}