test(confirm-service): normalise vi.mock spelling and remove duplicate-id mocks

Five test files mocked $lib/shared/services/confirm.svelte under BOTH
spellings (.svelte and .svelte.js) within the same file; two more mocked
only the .svelte.js form. Both resolve to the same module URL but register
two distinct Playwright route handlers in @vitest/browser-playwright. The
cleanup logic only removes one, leaving an orphan that fires when the next
session loads the module — crashing the run with
"[birpc] rpc is closed, cannot call resolveManualMock".

This is the exact trigger fixed upstream by vitest PR #10267 (issue #9957).
Normalise every confirm.svelte mock to the no-extension form, matching
production imports and the source file basename (confirm.svelte.ts).

After this commit: 8 confirm.svelte mocks across 8 spec files, all under
one canonical ID. A meta-test (next commit) prevents the duplicate-id
pattern from reappearing.

Refs: #553 · vitest-dev/vitest#9957 · vitest-dev/vitest#10267

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/lib/document/transcription/TranscriptionEditView.svelte.test.ts

@@ -5,9 +5,6 @@ import { page } from 'vitest/browser';
 vi.mock('$lib/shared/services/confirm.svelte', () => ({
 	getConfirmService: () => ({ confirm: async () => false })
 }));
-vi.mock('$lib/shared/services/confirm.svelte.js', () => ({
-	getConfirmService: () => ({ confirm: async () => false })
-}));
 
 const { default: TranscriptionEditView } = await import('./TranscriptionEditView.svelte');
 import type { TranscriptionBlockData } from '$lib/shared/types';