feat: complete SHD MCP plugin workflows and widget

.github/workflows/validate-plugin.yml

@@ -0,0 +1,24 @@
+name: Validate SHD MCP plugin
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+      - name: Validate package contracts
+        run: python -m unittest discover -s tests -v
+      - name: Verify widget checksum file
+        working-directory: plugins/shd-mcp-plugin/widgets/active-projects/v1
+        run: sha256sum --check SHA256SUMS