D2: JobErrorLine component + home/jobs page integration

- Add src/lib/components/JobErrorLine.svelte: reusable error banner with
  icon, truncated message, accent retry and danger delete buttons; Svelte 5
  runes; WCAG AA (role=alert/status, aria-busy, aria-label, focus ring)
- Integrate into src/routes/+page.svelte: replace .recent-err-line div with
  JobErrorLine; add handleRetry function updating jobs array in-place
- Integrate into src/routes/jobs/+page.svelte: remove inline .job-err-inline
  and .row-retry-slot; add JobErrorLine inside .job-info for failed/cancelled;
  refactor retryJobById/deleteJobById with clean (jobId: string) signatures;
  done-job delete preserved in row-actions
- Add src/tests/job-error-line.test.ts: 8 component rendering tests via
  @testing-library/svelte + happy-dom covering message, buttons, callbacks,
  fallback text, and ARIA roles
- Install @testing-library/svelte@5 and happy-dom as devDeps for component
  test support; update vitest.config.ts with svelte plugin, happy-dom env
  match glob, and browser resolve condition for Svelte 5 client build

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

vitest.config.ts

@@ -1,12 +1,17 @@
 import { defineConfig } from 'vitest/config';
+import { svelte } from '@sveltejs/vite-plugin-svelte';
 import path from 'path';
 
 export default defineConfig({
+	plugins: [svelte({ hot: false })],
 	test: {
 		environment: 'node',
 		globals: true,
 		fileParallelism: false,
 		include: ['src/tests/**/*.test.ts'],
+		environmentMatchGlobs: [
+			['**/job-error-line.test.ts', 'happy-dom']
+		],
 		coverage: {
 			provider: 'v8',
 			reporter: ['text', 'html'],
@@ -14,6 +19,7 @@ export default defineConfig({
 		}
 	},
 	resolve: {
+		conditions: ['browser'],
 		alias: {
 			'$lib': path.resolve('./src/lib')
 		}