ci: add e2e test workflow

Separate workflow for gateway e2e tests, runs on push/PR to main.
Same Python 3.11 + uv setup as existing tests.yml but targets only
tests/e2e/ with verbose output.

.github/workflows/e2e-tests.yml

@@ -0,0 +1,40 @@
+name: E2E Tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: e2e-tests-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  e2e:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Set up Python 3.11
+        run: uv python install 3.11
+
+      - name: Install dependencies
+        run: |
+          uv venv .venv --python 3.11
+          source .venv/bin/activate
+          uv pip install -e ".[all,dev]"
+
+      - name: Run e2e tests
+        run: |
+          source .venv/bin/activate
+          python -m pytest tests/e2e/ -v --tb=short
+        env:
+          OPENROUTER_API_KEY: ""
+          OPENAI_API_KEY: ""
+          NOUS_API_KEY: ""