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>

examples/dsh-agents-as-a-service/10-sandboxtemplate.yaml

@@ -50,20 +50,39 @@ spec:
             # gateway base URL if you want hard-coded absolute links instead.
             - name: DSH_PUBLIC_URL
               value: ""
+            # DSH Host/Origin-fences /api. The gateway forwards the browser's
+            # Host, so DSH must trust the public gateway host. Empty is right
+            # for port-forward/localhost; for the optional Ingress set this to
+            # the same host as 60-ingress.yaml (e.g. dsh.example.com).
+            - name: DSH_TRUSTED_HOSTS
+              value: ""
+          # Probes target /favicon.svg: DSH gates / behind its launch-token
+          # cookie and answers 401 to an unauthenticated GET, which would
+          # otherwise fail readiness and then get the pod killed by liveness.
+          # /favicon.svg is served without auth and is the cheapest liveness
+          # signal that proves the HTTP server is actually serving requests.
           readinessProbe:
             httpGet:
-              path: /
+              path: /favicon.svg
               port: 3080
             initialDelaySeconds: 5
             periodSeconds: 5
             failureThreshold: 30
           livenessProbe:
             httpGet:
-              path: /
+              path: /favicon.svg
               port: 3080
             initialDelaySeconds: 15
             periodSeconds: 15
             failureThreshold: 3
+          # The container only needs to serve HTTP; drop every capability and
+          # disallow privilege escalation. DSH writes only to DSH_HOME (PVC).
+          securityContext:
+            allowPrivilegeEscalation: false
+            capabilities:
+              drop: ["ALL"]
+            seccompProfile:
+              type: RuntimeDefault
           resources:
             requests: {cpu: 250m, memory: 512Mi}
             limits: {cpu: "1", memory: 1Gi}