Initial import of the CBDDC codebase with docs and tests. Add a .NET-focused gitignore to keep generated artifacts out of source control.

.github/workflows/ci.yml

@@ -0,0 +1,52 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 10.0.x
+
+      - name: Restore
+        run: dotnet restore CBDDC.slnx
+
+      - name: Build (Warnings as Errors)
+        run: dotnet build CBDDC.slnx --no-restore -warnaserror
+
+      - name: Test
+        run: dotnet test CBDDC.slnx --no-build
+
+      - name: Format Check
+        run: dotnet format CBDDC.slnx --verify-no-changes
+
+      - name: Vulnerability Audit
+        shell: bash
+        run: |
+          dotnet package list --project CBDDC.slnx --include-transitive --vulnerable --format json > vuln.json
+          if grep -q '"severity"' vuln.json; then
+            echo "Vulnerable packages detected."
+            cat vuln.json
+            exit 1
+          fi
+
+      - name: Deprecation Audit
+        shell: bash
+        run: |
+          dotnet package list --project CBDDC.slnx --deprecated > deprecated.txt
+          if grep -q "has the following deprecated packages" deprecated.txt; then
+            echo "Deprecated packages detected."
+            cat deprecated.txt
+            exit 1
+          fi