feat(coding-agent): add named-only filter toggle to /resume picker (#1128)

Adds Ctrl+N toggle to filter sessions by named-only vs all in the /resume picker.

- Add NameFilter type and filtering logic to session-selector-search.ts
- Add toggleSessionNamedFilter app keybinding (default: ctrl+n)
- Show Name: All/Named state in header
- Empty state mentions toggle keybinding as escape hatch
- Export hasSessionName() to avoid duplication

Co-authored-by: warren <warren.winter@gmail.com>

packages/coding-agent/src/core/keybindings.ts

@@ -25,6 +25,7 @@ export type AppAction =
 	| "selectModel"
 	| "expandTools"
 	| "toggleThinking"
+	| "toggleSessionNamedFilter"
 	| "externalEditor"
 	| "followUp"
 	| "dequeue"
@@ -59,6 +60,7 @@ export const DEFAULT_APP_KEYBINDINGS: Record<AppAction, KeyId | KeyId[]> = {
 	selectModel: "ctrl+l",
 	expandTools: "ctrl+o",
 	toggleThinking: "ctrl+t",
+	toggleSessionNamedFilter: "ctrl+n",
 	externalEditor: "ctrl+g",
 	followUp: "alt+enter",
 	dequeue: "alt+up",
@@ -88,6 +90,7 @@ const APP_ACTIONS: AppAction[] = [
 	"selectModel",
 	"expandTools",
 	"toggleThinking",
+	"toggleSessionNamedFilter",
 	"externalEditor",
 	"followUp",
 	"dequeue",