refactor: migrate ime composition handler to dependency injection

Replace direct IMECompositionHandler instantiation with dependency injection pattern to improve modularity and enable better testing. Add IME_COMPOSITION_HANDLER injection token and register singleton instance in bootstrap dependencies.

Changes:
- Define IME_COMPOSITION_HANDLER injection token in imeHandling.ts
- Register singleton IMECompositionHandler instance in deps.ts
- Update CommitMessageEditor and ReviewCreation to inject handler instead of creating new instances

Author: tdkn

apps/desktop/src/components/CommitMessageEditor.svelte

@@ -17,7 +17,7 @@
 	import { WORKTREE_SERVICE } from '$lib/worktree/worktreeService.svelte';
 	import { inject } from '@gitbutler/core/context';
 	import { Button, TestId } from '@gitbutler/ui';
-	import { IMECompositionHandler } from '@gitbutler/ui/utils/imeHandling';
+	import { IME_COMPOSITION_HANDLER } from '@gitbutler/ui/utils/imeHandling';
 
 	import { tick } from 'svelte';
 
@@ -69,7 +69,7 @@
 
 	let composer = $state<ReturnType<typeof MessageEditor>>();
 	let titleInput = $state<HTMLTextAreaElement>();
-	const imeHandler = new IMECompositionHandler();
+	const imeHandler = inject(IME_COMPOSITION_HANDLER);
 
 	const suggestionsHandler = new CommitSuggestions(aiService, uiState);
 	const diffInputArgs = $derived<DiffInputContextArgs>(

apps/desktop/src/components/ReviewCreation.svelte

@@ -36,7 +36,7 @@
 	import { inject } from '@gitbutler/core/context';
 	import { persisted } from '@gitbutler/shared/persisted';
 	import { chipToasts, TestId } from '@gitbutler/ui';
-	import { IMECompositionHandler } from '@gitbutler/ui/utils/imeHandling';
+	import { IME_COMPOSITION_HANDLER } from '@gitbutler/ui/utils/imeHandling';
 	import { isDefined } from '@gitbutler/ui/utils/typeguards';
 	import { tick } from 'svelte';
 
@@ -92,7 +92,7 @@
 
 	let titleInput = $state<HTMLTextAreaElement | undefined>(undefined);
 	let messageEditor = $state<MessageEditor>();
-	const imeHandler = new IMECompositionHandler();
+	const imeHandler = inject(IME_COMPOSITION_HANDLER);
 
 	// AI things
 	const aiGenEnabled = projectAiGenEnabled(projectId);

apps/desktop/src/lib/bootstrap/deps.ts

@@ -82,6 +82,7 @@ import {
 	EXTERNAL_LINK_SERVICE,
 	type ExternalLinkService
 } from '@gitbutler/ui/utils/externalLinkService';
+import { IMECompositionHandler, IME_COMPOSITION_HANDLER } from '@gitbutler/ui/utils/imeHandling';
 import { PUBLIC_API_BASE_URL } from '$env/static/public';
 
 export function initDependencies(args: {
@@ -260,6 +261,7 @@ export function initDependencies(args: {
 	// ============================================================================
 
 	const focusManager = new FocusManager();
+	const imeHandler = new IMECompositionHandler();
 	const reorderDropzoneFactory = new ReorderDropzoneFactory(stackService);
 	const shortcutService = new ShortcutService(backend);
 	const dragStateService = new DragStateService();
@@ -326,6 +328,7 @@ export function initDependencies(args: {
 		[HOOKS_SERVICE, hooksService],
 		[HTTP_CLIENT, httpClient],
 		[ID_SELECTION, idSelection],
+		[IME_COMPOSITION_HANDLER, imeHandler],
 		[IRC_CLIENT, ircClient],
 		[IRC_SERVICE, ircService],
 		[MODE_SERVICE, modeService],

packages/ui/src/lib/utils/imeHandling.ts

@@ -1,3 +1,8 @@
+import { InjectionToken } from '@gitbutler/core/context';
+
+export const IME_COMPOSITION_HANDLER: InjectionToken<IMECompositionHandler> =
+	new InjectionToken<IMECompositionHandler>('IMECompositionHandler');
+
 /**
  * IME (Input Method Editor) handling utilities for text input components.
  * This class provides a unified handler to manage IME composition state