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/core/keybindings.ts

@@ -27,7 +27,8 @@ export type AppAction =
 	| "toggleThinking"
 	| "externalEditor"
 	| "followUp"
-	| "dequeue";
+	| "dequeue"
+	| "pasteImage";
 
 /**
  * All configurable actions.
@@ -58,6 +59,7 @@ export const DEFAULT_APP_KEYBINDINGS: Record<AppAction, KeyId | KeyId[]> = {
 	externalEditor: "ctrl+g",
 	followUp: "alt+enter",
 	dequeue: "alt+up",
+	pasteImage: "ctrl+v",
 };
 
 /**
@@ -83,6 +85,7 @@ const APP_ACTIONS: AppAction[] = [
 	"externalEditor",
 	"followUp",
 	"dequeue",
+	"pasteImage",
 ];
 
 function isAppAction(action: string): action is AppAction {
@@ -175,16 +178,6 @@ export class KeybindingsManager {
 		return this.appActionToKeys.get(action) ?? [];
 	}
 
-	/**
-	 * Get display string for an action.
-	 */
-	getDisplayString(action: AppAction): string {
-		const keys = this.getKeys(action);
-		if (keys.length === 0) return "";
-		if (keys.length === 1) return keys[0]!;
-		return keys.join("/");
-	}
-
 	/**
 	 * Get the full effective config.
 	 */