fix(s6): reserved default gateway must not follow sticky active_profile (#46483)

The supervised `gateway-default` s6 slot runs bare `hermes gateway run`
(no -p) to mean "the root HERMES_HOME profile". But `_apply_profile_override`
falls through its #22502 HERMES_HOME guard for the container root
(/opt/data, whose parent is not `profiles`) and reads the sticky
`active_profile` file. If the user set another profile active (e.g. via
the dashboard), the reserved default gateway gets redirected into that
profile — producing a duplicate gateway for the active profile and no
real default gateway. The profile page and `gateway status` then
correctly report default as "not running" because there genuinely isn't
one.

Guard step 2 (the sticky active_profile fallback) with the existing
HERMES_S6_SUPERVISED_CHILD sentinel that the container run-script already
exports. Supervised named-profile slots pass -p explicitly (step 1, never
reaches step 2); only the bare default slot was affected. Inert outside
the s6 container — the sentinel is never set elsewhere.

Reported in the 'Docker & Profiles & Dashboard' support thread.

hermes_cli/main.py

@@ -452,8 +452,19 @@ def _apply_profile_override() -> None:
         if Path(hermes_home_env).parent.name == "profiles":
             return
 
-    # 2. If no flag, check active_profile in the hermes root
-    if profile_name is None:
+    # 2. If no flag, check active_profile in the hermes root.
+    #
+    # EXCEPTION: a supervised s6 gateway child (exported by the container
+    # run-script as HERMES_S6_SUPERVISED_CHILD=1) must NOT follow the sticky
+    # active_profile. Each supervised slot has a fixed profile identity: named
+    # slots pass ``-p <name>`` explicitly (handled in step 1 above), and the
+    # reserved ``gateway-default`` slot runs bare ``hermes gateway run`` to mean
+    # "the root HERMES_HOME profile". If the reserved default child read
+    # active_profile here, switching the active profile (e.g. via the dashboard)
+    # would silently redirect the default gateway into that profile — yielding a
+    # duplicate gateway for the active profile and no real default gateway. See
+    # the "Docker & Profiles & Dashboard" report.
+    if profile_name is None and not os.environ.get("HERMES_S6_SUPERVISED_CHILD"):
         try:
             from hermes_constants import get_default_hermes_root