The Docker integration test job started failing on main after
fb51253 ("docker: opt in to dashboard --insecure via env var").
Two distinct failures, both fallout from that change being more
behaviour-changing than the existing test harness anticipated.

Failure 1 — test_dashboard_port_override (silent regression in an
already-existing test)
The test starts the container with just HERMES_DASHBOARD=1, defaults
to host=0.0.0.0, no HERMES_DASHBOARD_OAUTH_CLIENT_ID, no
HERMES_DASHBOARD_INSECURE. Pre-fix that combination got --insecure
auto-injected by the s6 run script (anything non-loopback was
implicitly insecure), so the OAuth gate stayed off and start_server
bound the port. Post-fix the gate engages, no provider is
registered, and start_server raises SystemExit before binding —
under s6 the dashboard goes into a restart loop and the test's
/proc/net/tcp poll finds nothing.

Same silent regression was masking three sibling tests
(test_dashboard_slot_reports_up_when_enabled, test_dashboard_opt_in_starts,
test_dashboard_restarts_after_crash) — they all only sample pgrep
or s6-svstat and so caught the supervised process mid-restart
loop, appearing to pass while the dashboard was actually never
reaching a healthy state.

Fix: pin HERMES_DASHBOARD_INSECURE=1 on every test that enables
the dashboard but doesn't itself exercise the auth gate. Each
pinned site carries an inline comment pointing back to
test_dashboard_slot_reports_up_when_enabled for the full
rationale.

Failure 2 — test_dashboard_oauth_gate_engages_on_non_loopback_bind
(bug in the test I added in fb51253)
The probe used urllib.request.urlopen() against /api/status. Under
the now-engaged OAuth gate /api/status no longer answers
unauthenticated callers (the gate middleware runs upstream of the
legacy _SESSION_TOKEN allowlist and 401s anything without a valid
session cookie). urlopen() raises HTTPError on the 401, the wrapper
treated that as "not ready yet", and the poll loop hit
timeout.

Fix: split the probe into a generic _http_probe() helper that
returns (status_code, body) for any HTTP response — including 401,
which IS the gate-engaged success signal. The helper feeds a
multi-line Python program over stdin via a POSIX heredoc so the
try/except branch reads naturally; far less fragile than the
earlier semicolon-laden -c one-liner.

The OAuth-gate test now verifies two independent observable
consequences of the gate being on:

  1. GET /api/auth/providers (publicly reachable through the gate
     so the login page can bootstrap) returns 200 with `nous` in
     the provider list — proves the bundled provider registered.
  2. GET /api/status returns 401 — proves the OAuth gate runs
     upstream of the legacy public-paths allowlist and is
     actively intercepting unauthenticated callers.

The insecure-opt-out test still hits /api/status, but now
asserts status_code == 200 first (proves the gate is bypassed)
before parsing the JSON for auth_required: false (proves the
gate-state flag is also correctly off).

Verified locally end-to-end against a fresh image build on a
real Docker daemon: all 41 tests under tests/docker/ pass in
2m38s, including the two formerly-failing dashboard tests and
the three sibling tests that were passing by accident.