fix(coding-agent): fix IME candidate window positioning in menu selectors

Components with search inputs now implement Focusable interface and
propagate focus state to their child Input components. This allows
the hardware cursor to be positioned correctly for IME candidate
window placement.

Affected components:
- ModelSelectorComponent
- ScopedModelsSelectorComponent
- SessionSelectorComponent (and SessionList)
- ExtensionInputComponent
- LoginDialogComponent
- TreeSelectorComponent (and LabelInput)

fixes #827

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

@@ -1,6 +1,7 @@
 import type { Model } from "@mariozechner/pi-ai";
 import {
 	Container,
+	type Focusable,
 	fuzzyFilter,
 	getEditorKeybindings,
 	Input,
@@ -92,13 +93,23 @@ export interface ModelsCallbacks {
  * Component for enabling/disabling models for Ctrl+P cycling.
  * Changes are session-only until explicitly persisted with Ctrl+S.
  */
-export class ScopedModelsSelectorComponent extends Container {
+export class ScopedModelsSelectorComponent extends Container implements Focusable {
 	private modelsById: Map<string, Model<any>> = new Map();
 	private allIds: string[] = [];
 	private enabledIds: EnabledIds = null;
 	private filteredItems: ModelItem[] = [];
 	private selectedIndex = 0;
 	private searchInput: Input;
+
+	// Focusable implementation - propagate to searchInput for IME cursor positioning
+	private _focused = false;
+	get focused(): boolean {
+		return this._focused;
+	}
+	set focused(value: boolean) {
+		this._focused = value;
+		this.searchInput.focused = value;
+	}
 	private listContainer: Container;
 	private footerText: Text;
 	private callbacks: ModelsCallbacks;