Add multiselect board filters and letter-jump on picker menus.

Persist comma-separated list filters per project, toggle with space, and jump by first letter in board and project pickers.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/ui/keys.go

@@ -16,6 +16,7 @@ type KeyMap struct {
 	Delete        key.Binding // x — confirm first
 	DeleteForce   key.Binding // X — immediate
 	ConfirmYes    key.Binding
+	Toggle        key.Binding // space — toggle multi-select
 	Undo          key.Binding
 	Redo          key.Binding
 	Quit          key.Binding
@@ -74,6 +75,10 @@ func DefaultKeyMap() KeyMap {
 			key.WithKeys("y", "Y"),
 			key.WithHelp("y", "confirm"),
 		),
+		Toggle: key.NewBinding(
+			key.WithKeys(" "),
+			key.WithHelp("space", "toggle"),
+		),
 		Undo: key.NewBinding(
 			key.WithKeys("u", "ctrl+z"),
 			key.WithHelp("u", "undo"),