Make DSH agents-as-a-service browser-usable; fix probe crash-loop (#3)

* Rewrite DSH gateway for browser sessions, HTTP and WebSocket

- Replace the Flask proxy with a Starlette ASGI app (uvicorn factory),
  keeping the control plane (claims, wake/suspend, idle sweeper).
- Add HttpOnly gateway sessions and a server-side DSH launch-token
  handshake: read the token from pod logs, exchange it for a dsh-auth
  cookie, cache per (user, pod UID, Host), refresh once on 401.
- Proxy HTTP/SSE and WebSocket (/api/remote.mux) under /u/<user>/, with
  header stripping/injection, Location rewriting and wake-on-connect.
- Add a landing/signup/login page, health endpoint, pinned dependencies,
  a read-only-rootfs gateway image, 87 cluster-free tests and docs.

* Fix DSH probe crash-loop and harden gateway manifests

- Probe /favicon.svg instead of /: DSH gates / behind its launch-token
  cookie and returns 401, which made warm-pool pods crash-loop.
- Pass DSH_TRUSTED_HOSTS through the entrypoint as --trusted-host args
  for public/ingress hosts; keep localhost trusted.
- Deploy the published :gateway image, add pods/pods-log RBAC, /healthz
  probes, read-only rootfs with a /tmp emptyDir and non-root security.
- Add optional Traefik Ingress and document the prerequisites.

* Update CI, smoke tests, build tooling and docs

- Run gateway pytest/ruff and build/smoke-test the image in CI.
- Parameterize the DSH build version and pnpm version inputs.
- Exercise cookie signup, HTML proxy, WebSocket auth, suspend/wake and
  delete in run-test-kind.sh.
- Add Makefile/build.sh targets and document the architecture, handshake,
  probes, trusted hosts, troubleshooting and limitations.

---------

Co-authored-by: SREDevOpsAgents <agents@sredevops.org>

.github/workflows/validate.yaml

@@ -1,8 +1,9 @@
 name: Validate
 
 # Validates the Kubernetes manifests against the real agent-sandbox CRD
-# schema (server-side dry-run on a throwaway kind cluster) and runs the
-# gateway unit tests. Runs on every PR and on pushes to main.
+# schema (server-side dry-run on a throwaway kind cluster), runs the gateway
+# unit tests + lint, and builds/smoke-tests the gateway image without a
+# cluster. Runs on every PR and on pushes to main.
 on:
   pull_request:
   push:
@@ -45,6 +46,10 @@ jobs:
           echo "all manifests validated"
 
   gateway-tests:
+    # The gateway lives in examples/dsh-agents-as-a-service/gateway/. Its
+    # runtime pins and dev pins are kept separate so the image only ships
+    # requirements.txt while CI installs both files.
+    name: Gateway unit tests and lint
     runs-on: ubuntu-latest
     defaults:
       run:
@@ -57,9 +62,76 @@ jobs:
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         with:
           python-version: "3.12"
+          cache: pip
+          cache-dependency-path: |
+            examples/dsh-agents-as-a-service/gateway/requirements.txt
+            examples/dsh-agents-as-a-service/gateway/requirements-dev.txt
 
       - name: Install dependencies
-        run: pip install -r requirements.txt pytest
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements.txt -r requirements-dev.txt
+
+      - name: Lint (ruff)
+        run: python -m ruff check .
 
       - name: Run gateway unit tests
-        run: python -m pytest test_gateway.py -v
+        run: python -m pytest -v
+
+  gateway-image:
+    # No cluster and no real credentials: the gateway must start and answer
+    # /healthz with a dummy kubeconfig, which catches broken imports, missing
+    # runtime deps, and an unresponsive ASGI entrypoint.
+    name: Build and smoke-test gateway image
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Build gateway image
+        run: |
+          docker build \
+            -t dsh-aaas-gateway:ci \
+            examples/dsh-agents-as-a-service/gateway/
+
+      - name: Smoke-test /healthz without a cluster
+        run: |
+          set -euo pipefail
+          cat > /tmp/kubeconfig <<'EOF'
+          apiVersion: v1
+          kind: Config
+          clusters:
+            - name: dummy
+              cluster:
+                server: https://127.0.0.1:6443
+                insecure-skip-tls-verify: true
+          contexts:
+            - name: dummy
+              context:
+                cluster: dummy
+                user: dummy
+          users:
+            - name: dummy
+              user: {}
+          current-context: dummy
+          EOF
+          docker run -d --name gateway-smoke \
+            -p 18080:8080 \
+            -e NAMESPACE=dsh-demo \
+            -e POOL=dsh-pool \
+            -e KUBECONFIG=/tmp/kubeconfig \
+            -v /tmp/kubeconfig:/tmp/kubeconfig:ro \
+            dsh-aaas-gateway:ci
+          trap 'docker logs gateway-smoke || true; docker rm -f gateway-smoke || true' EXIT
+
+          code=""
+          for _ in $(seq 1 30); do
+            code=$(curl -s -o /dev/null -w '%{http_code}' http://localhost:18080/healthz || true)
+            [ "$code" = "200" ] && break
+            sleep 1
+          done
+          if [ "$code" != "200" ]; then
+            echo "gateway /healthz returned '$code' instead of 200" >&2
+            exit 1
+          fi
+          echo "gateway image healthy: GET /healthz -> 200"