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>

.antigravityrules

@@ -3,11 +3,12 @@
 All AI agents (including Cline, Antigravity, Cursor, and Copilot) must adhere to the following rules before declaring a task complete:
 
 1. **Test Coverage (>= 80%)**:
-   - The overall project code coverage (Statements, Lines, and Functions) must be maintained at **80% or higher**.
+   - The overall project line coverage must be maintained at **80% or higher**. Bun reports line data only; statement, branch and function coverage are no longer measured.
    - Verify coverage by running:
      ```bash
      bun scripts/generate-langs.js
-     NODE_OPTIONS=--max-old-space-size=2048 bunx vitest run --coverage --maxWorkers=1 --exclude='src/app/benchmark/**'
+     bun test --config=bunfig.coverage.toml --isolate --path-ignore-patterns='**/benchmark/**'
+     bun scripts/coverage-reports.mjs
      ```
    - If your changes introduce new code or modify existing code in a way that drops the coverage below 80%, you must write appropriate unit tests in `.spec.ts` files to bring it back up.
 
@@ -33,4 +34,4 @@ All AI agents (including Cline, Antigravity, Cursor, and Copilot) must adhere to
      - **Unit Tests and Coverage**: generate the language registry, then run the coverage command in rule 1, matching the Gitea functional-test job.
      - **CI policy and publication**: `node scripts/ci-policy.test.mjs` and `node scripts/ci-image.test.mjs`
      - **Production Build**: `bun run build -- --configuration production`
-   - The separate performance benchmark is a required CI job with a relative gate: each scenario's budget is a multiple of the frozen engine's two-year calibration measured in the same run. Run it outside coverage with `NODE_OPTIONS=--max-old-space-size=2048 bunx vitest run src/app/benchmark/ --maxWorkers=1` when verifying performance; see `docs/benchmark/README.md`.
+   - The separate performance benchmark is a required CI job with a relative gate: each scenario's budget is a multiple of the frozen engine's two-year calibration measured in the same run. Run it outside coverage with `timeout 600s bun test src/app/benchmark --timeout=600000` when verifying performance; see `docs/benchmark/README.md`.