ci: add install-only workflow for manual dependency install checks

.github/workflows/install-only.yml

@@ -0,0 +1,42 @@
+name: Install-only CI
+
+on:
+  workflow_dispatch: {}
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  install-only:
+    name: Install-only
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.10, 3.11]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Upgrade pip tooling
+        run: |
+          python -m pip install --upgrade pip setuptools wheel
+
+      - name: Install project extras (install-only)
+        env:
+          PIP_DISABLE_PIP_VERSION_CHECK: '1'
+        run: |
+          # Install editable with the same extras used in the full CI
+          pip install -e ".[test,graph,vector_stores,llms,extras]"
+
+      - name: Run pip check
+        run: |
+          # Show any dependency conflicts (non-zero exit will mark job failed)
+          pip check
+
+      - name: Show installed packages summary
+        run: |
+          pip list --format=columns