test: run the suite and benchmark with Bun's native test runner

Replace Vitest with bun test across the whole suite. A preload compiles
components through Angular's JIT transform with inlined templates, sets
up jsdom, TestBed and zoneless change detection, and a small shim covers
the Vitest APIs bun:test lacks. Files run isolated, real-worker specs
spawn the running Bun, and line coverage from lcov is converted to the
existing HTML and Cobertura reports. The CI benchmark replaces its heap
cap with a container memory limit. Vitest, Jest, Nx and their Vite
configuration are removed.

Refs #291

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/coverage-reports.mjs

@@ -0,0 +1,31 @@
+// Converts coverage/lcov.info (Bun) to HTML and Cobertura. Run: bun scripts/coverage-reports.mjs
+// shortcut: line coverage only, Bun's lcov has no usable branch/function data; revisit if Bun adds it.
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import libCoverage from 'istanbul-lib-coverage';
+import libReport from 'istanbul-lib-report';
+import reports from 'istanbul-reports';
+
+const map = libCoverage.createCoverageMap({});
+const loc = (line) => ({ start: { line, column: 0 }, end: { line, column: 1 } });
+for (const record of readFileSync('coverage/lcov.info', 'utf8').split('end_of_record')) {
+	const file = /^SF:(.+)$/m.exec(record)?.[1];
+	if (!file) continue;
+	const statementMap = {};
+	const s = {};
+	for (const [, line, hits] of record.matchAll(/^DA:(\d+),(\d+)/gm)) {
+		statementMap[line] = loc(+line);
+		s[line] = +hits;
+	}
+	map.addFileCoverage({
+		path: resolve(file),
+		statementMap,
+		s,
+		fnMap: {},
+		f: {},
+		branchMap: {},
+		b: {},
+	});
+}
+const context = libReport.createContext({ dir: 'coverage', coverageMap: map });
+for (const name of ['html', 'cobertura']) reports.create(name).execute(context);