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>

tsconfig.spec.json

@@ -2,7 +2,7 @@
 	"extends": "./tsconfig.json",
 	"compilerOptions": {
 		"outDir": "./out-tsc/spec",
-		"types": ["vitest/globals"],
+		"types": ["bun", "bun-types/test-globals", "node"],
 		"target": "es2022"
 	},
 	"include": ["src/**/*.ts"],