fix(test): extend coverage thresholds to all four dimensions

Add lines, functions, and statements at 80% alongside branches in both
the server (vite.config.ts) and client (vitest.client-coverage.config.ts)
coverage gates — branch-only thresholds allow misleadingly sparse tests to
pass the gate.

Also adds a plugin-sync comment to vitest.client-coverage.config.ts listing
the four Vite plugins mirrored from vite.config.ts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -59,7 +59,10 @@ export default defineConfig({
 			],
 			exclude: ['**/*.svelte', '**/*.svelte.ts', '**/__mocks__/**'],
 			thresholds: {
-				branches: 80
+				lines: 80,
+				functions: 80,
+				branches: 80,
+				statements: 80
 			}
 		},
 		projects: [

frontend/vitest.client-coverage.config.ts

@@ -8,6 +8,8 @@ import { sveltekit } from '@sveltejs/kit/vite';
 // Standalone config for browser-project Istanbul coverage.
 // Uses a dedicated root-level coverage block because Vitest 4 ignores
 // per-project coverage overrides inside test.projects.
+// Plugins mirrored from vite.config.ts: tailwindcss, sveltekit, devtoolsJson, paraglideVitePlugin
+// Update here whenever vite.config.ts plugins change.
 export default defineConfig({
 	optimizeDeps: {
 		include: ['pdfjs-dist', '@tiptap/core', '@tiptap/starter-kit', '@tiptap/extension-mention']
@@ -39,7 +41,10 @@ export default defineConfig({
 			include: ['src/**/*.svelte', 'src/**/*.svelte.ts'],
 			exclude: ['src/lib/paraglide/**', 'src/lib/generated/**', 'src/hooks/**', '**/__mocks__/**'],
 			thresholds: {
-				branches: 80
+				lines: 80,
+				functions: 80,
+				branches: 80,
+				statements: 80
 			}
 		}
 	}