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/keys.go

@@ -0,0 +1,92 @@
+package tui
+
+import "github.com/charmbracelet/bubbles/key"
+
+type keyMap struct {
+	Left    key.Binding
+	Right   key.Binding
+	Up      key.Binding
+	Down    key.Binding
+	Enter   key.Binding
+	Edit    key.Binding
+	New     key.Binding
+	Done    key.Binding
+	Wontdo  key.Binding
+	Refresh key.Binding
+	Filter  key.Binding
+	Help    key.Binding
+	Quit    key.Binding
+	Back    key.Binding
+}
+
+var keys = keyMap{
+	Left: key.NewBinding(
+		key.WithKeys("h", "left"),
+		key.WithHelp("h/←", "prev column"),
+	),
+	Right: key.NewBinding(
+		key.WithKeys("l", "right"),
+		key.WithHelp("l/→", "next column"),
+	),
+	Up: key.NewBinding(
+		key.WithKeys("k", "up"),
+		key.WithHelp("k/↑", "up"),
+	),
+	Down: key.NewBinding(
+		key.WithKeys("j", "down"),
+		key.WithHelp("j/↓", "down"),
+	),
+	Enter: key.NewBinding(
+		key.WithKeys("enter"),
+		key.WithHelp("enter", "detail"),
+	),
+	Edit: key.NewBinding(
+		key.WithKeys("e"),
+		key.WithHelp("e", "edit"),
+	),
+	New: key.NewBinding(
+		key.WithKeys("n"),
+		key.WithHelp("n", "new task"),
+	),
+	Done: key.NewBinding(
+		key.WithKeys("d"),
+		key.WithHelp("d", "mark done"),
+	),
+	Wontdo: key.NewBinding(
+		key.WithKeys("w"),
+		key.WithHelp("w", "mark wontdo"),
+	),
+	Refresh: key.NewBinding(
+		key.WithKeys("r"),
+		key.WithHelp("r", "refresh"),
+	),
+	Filter: key.NewBinding(
+		key.WithKeys("/"),
+		key.WithHelp("/", "filter repo"),
+	),
+	Help: key.NewBinding(
+		key.WithKeys("?"),
+		key.WithHelp("?", "help"),
+	),
+	Quit: key.NewBinding(
+		key.WithKeys("q", "ctrl+c"),
+		key.WithHelp("q", "quit"),
+	),
+	Back: key.NewBinding(
+		key.WithKeys("esc"),
+		key.WithHelp("esc", "back"),
+	),
+}
+
+func (k keyMap) ShortHelp() []key.Binding {
+	return []key.Binding{k.Left, k.Right, k.Up, k.Down, k.Enter, k.Edit, k.New, k.Done, k.Quit, k.Help}
+}
+
+func (k keyMap) FullHelp() [][]key.Binding {
+	return [][]key.Binding{
+		{k.Left, k.Right, k.Up, k.Down},
+		{k.Enter, k.Edit, k.New, k.Refresh},
+		{k.Done, k.Wontdo, k.Filter},
+		{k.Quit, k.Back, k.Help},
+	}
+}