feat: add KinD integration tests

Add integration tests that run against a real Kubernetes cluster using
KinD (Kubernetes in Docker). This addresses #58.

Changes:
- Add integration_test.go with tests for:
  - Pod events (create/delete)
  - ReplicaSet events
  - Multi-namespace support
  - Label selector filtering
- Add .github/workflows/integration.yaml CI workflow that:
  - Runs lint and unit tests first
  - Then runs integration tests with KinD
  - 10 minute timeout
- Add scripts/kind-setup.sh for local development
- Update README.md with integration test documentation

The integration tests use the existing fakeAgentAPI to mock the Coder
server, focusing on validating real Kubernetes informer behavior.

Author: kacpersaw

.github/workflows/integration.yaml

@@ -0,0 +1,61 @@
+name: integration
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  actions: none
+  checks: none
+  contents: read
+  deployments: none
+  issues: none
+  packages: none
+  pull-requests: none
+  repository-projects: none
+  security-events: none
+  statuses: none
+
+# Cancel in-progress runs for pull requests when developers push
+# additional changes
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+jobs:
+  unit-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "~1.22"
+
+      - name: Test
+        run: go test ./... -race
+
+  integration-test:
+    needs: [unit-test]
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "~1.22"
+
+      - name: Create KinD cluster
+        uses: helm/kind-action@v1
+        with:
+          cluster_name: integration-test
+
+      - name: Run integration tests
+        run: go test -tags=integration -v -timeout=8m ./...

README.md

@@ -64,3 +64,42 @@ Kubernetes provides an [informers](https://pkg.go.dev/k8s.io/client-go/informers
 
 - [`SSL_CERT_FILE`](https://go.dev/src/crypto/x509/root_unix.go#L19): Specifies the path to an SSL certificate.
 - [`SSL_CERT_DIR`](https://go.dev/src/crypto/x509/root_unix.go#L25): Identifies which directory to check for SSL certificate files.
+
+## Development
+
+### Running Tests
+
+Unit tests can be run with:
+
+```console
+go test ./... -race
+```
+
+### Integration Tests
+
+Integration tests run against a real Kubernetes cluster using [KinD (Kubernetes in Docker)](https://kind.sigs.k8s.io/).
+
+**Prerequisites:**
+- [Docker](https://docs.docker.com/get-docker/)
+- [KinD](https://kind.sigs.k8s.io/docs/user/quick-start/#installation)
+- [kubectl](https://kubernetes.io/docs/tasks/tools/)
+
+**Setup and run:**
+
+```console
+# Create a KinD cluster
+./scripts/kind-setup.sh create
+
+# Run integration tests
+go test -tags=integration -v ./...
+
+# Clean up when done
+./scripts/kind-setup.sh delete
+```
+
+The integration tests validate:
+- Pod event streaming with real Kubernetes informers
+- ReplicaSet event handling
+- Multi-namespace support
+- Label selector filtering
+