ci: run the integration suites inside the stack's own network

The suites connected to localhost:<published port>, which works for a developer
but not on a containerised runner: published ports live in the host's network
namespace, so the runner container gets connection refused.

Run them from inside the stack instead, against the gateway by service name.
SITE_BASE_URL and SITE_HOST_HEADER make that possible without weakening what is
under test: the Host stays "localhost", so the gateway's host check and
TrustedHostMiddleware see exactly what a localhost run produces, and the tests
that deliberately send their own Host still override it.

S3_PUBLIC_ENDPOINT has to agree, because presigned URLs are signed against it
and the signature covers the host, so it cannot be rewritten afterwards. CI
points the whole stack at http://storage:9000 so the URLs it hands out are
reachable by whoever follows them.

The browser suites still need Chrome to reach the stack from the runner, which
the same namespace split prevents. They now check reachability and skip with a
warning instead of failing with a bare connection error; recorded as ROADMAP
5.10, since they are the only coverage for the artwork editor.

Verified both ways: the six suites pass inside the network, and an unchanged
developer localhost run still passes, as do both browser suites locally.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ROADMAP.md

@@ -364,6 +364,14 @@ charges. Fix as part of 1.1.
   table and the packer so 3.2 has somewhere to land.
 - `[ ]` 5.7 — Commercial rules duplicated between `FAIXAS` (JS) and `TIERS` (Python)
   `(F26)`. `test_pricing` guards parity; generate one from the other instead.
+- `[ ]` 5.10 — The browser suites do not run in CI. Chrome runs in the runner
+  container and can only reach the stack through ports published on the host, which
+  is a different network namespace when the runner is itself a container. The API,
+  workflow, security, scanning, retention and runtime suites were moved inside the
+  stack's network and do gate. The browser suites are the only coverage for the
+  artwork editor and the full customer journey, so they need either Chrome in a
+  container on that network, or a runner with host networking. Until then they gate
+  locally only, and CI warns when it skips them.
 - `[ ]` 5.9 — `local/browser_test.mjs` failed once and passed on an immediate
   re-run, with no code change in between (2026-09-21). It is a deploy gate when the
   runner has Chrome, so an intermittent failure there blocks releases for no reason.