refactor: use configurable keybindings for all UI hints (#724)

Follow-up to #717. Replaces all remaining hardcoded keybinding hints with configurable ones.

- Add pasteImage to AppAction so it can be configured in keybindings.json
- Create keybinding-hints.ts with reusable helper functions:
  - editorKey(action) / appKey(keybindings, action) - get key display string
  - keyHint(action, desc) / appKeyHint(kb, action, desc) / rawKeyHint(key, desc) - styled hints
- Export helpers from components/index.ts for extensions
- Update all components to use configured keybindings
- Remove now-unused getDisplayString() from KeybindingsManager and EditorKeybindingsManager
- Use keybindings.matches() instead of matchesKey() for pasteImage in custom-editor.ts

packages/coding-agent/src/modes/interactive/components/extension-selector.ts

@@ -7,6 +7,7 @@ import { Container, getEditorKeybindings, Spacer, Text, type TUI } from "@marioz
 import { theme } from "../theme/theme.js";
 import { CountdownTimer } from "./countdown-timer.js";
 import { DynamicBorder } from "./dynamic-border.js";
+import { keyHint, rawKeyHint } from "./keybinding-hints.js";
 
 export interface ExtensionSelectorOptions {
 	tui?: TUI;
@@ -56,7 +57,17 @@ export class ExtensionSelectorComponent extends Container {
 		this.listContainer = new Container();
 		this.addChild(this.listContainer);
 		this.addChild(new Spacer(1));
-		this.addChild(new Text(theme.fg("dim", "↑↓ navigate  enter select  esc cancel"), 1, 0));
+		this.addChild(
+			new Text(
+				rawKeyHint("↑↓", "navigate") +
+					"  " +
+					keyHint("selectConfirm", "select") +
+					"  " +
+					keyHint("selectCancel", "cancel"),
+				1,
+				0,
+			),
+		);
 		this.addChild(new Spacer(1));
 		this.addChild(new DynamicBorder());