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>

bunfig.coverage.toml

@@ -0,0 +1,8 @@
+[test]
+preload = ["./src/test-setup.ts"]
+root = "src"
+coverage = true
+coverageReporter = ["text", "lcov"]
+coverageDir = "coverage"
+coverageSkipTestFiles = true
+coveragePathIgnorePatterns = ["**/frozen-engine/**", "**/testing/**", "**/test-setup.ts"]