feat: add CI workflow for building CLI with Nx commands

This adds a new GitHub Actions workflow build-cli-nx.yml that builds
the CLI using Nx commands instead of npm scripts. Key differences:

- Uses `npx nx build cli --configuration=oss/bit` instead of npm run dist commands
- Simplified build matrix focusing on OSS/Bit configurations
- Runs build, test, and lint targets through Nx
- Working directory is repo root instead of apps/cli
- Removes platform-specific packaging (focusing on basic build verification)

This complements the existing build-cli.yml workflow and allows us to
validate that our Nx integration works in CI while keeping the existing
npm-based builds as the primary deployment mechanism.

The workflow validates both OSS and Bit configurations and ensures the
build output is functional by testing the CLI help command.

.github/workflows/nx.yml

@@ -0,0 +1,21 @@
+name: Experimental Nx CI
+on:
+  pull_request:
+    paths:
+      - 'apps/cli/**'
+      - 'libs/**'
+  
+jobs:
+  nx-experiment:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: 'npm'
+      - run: npm ci
+      - uses: nrwl/nx-set-shas@v4
+      - run: npx nx affected -t build lint test