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/model-selector.ts

@@ -1,5 +1,14 @@
 import { type Model, modelsAreEqual } from "@mariozechner/pi-ai";
-import { Container, fuzzyFilter, getEditorKeybindings, Input, Spacer, Text, type TUI } from "@mariozechner/pi-tui";
+import {
+	Container,
+	type Focusable,
+	fuzzyFilter,
+	getEditorKeybindings,
+	Input,
+	Spacer,
+	Text,
+	type TUI,
+} from "@mariozechner/pi-tui";
 import type { ModelRegistry } from "../../../core/model-registry.js";
 import type { SettingsManager } from "../../../core/settings-manager.js";
 import { theme } from "../theme/theme.js";
@@ -19,8 +28,18 @@ interface ScopedModelItem {
 /**
  * Component that renders a model selector with search
  */
-export class ModelSelectorComponent extends Container {
+export class ModelSelectorComponent extends Container implements Focusable {
 	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 allModels: ModelItem[] = [];
 	private filteredModels: ModelItem[] = [];