fix: profile paths broken in Docker — profiles go to /root/.hermes instead of mounted volume (#7170)

In Docker, HERMES_HOME=/opt/data (set in Dockerfile) and users mount
their .hermes directory to /opt/data. However, profile operations used
Path.home() / '.hermes' which resolves to /root/.hermes in Docker —
an ephemeral container path, not the mounted volume.

This caused:
- Profiles created at /root/.hermes/profiles/ (lost on container recreate)
- active_profile sticky file written to wrong location
- profile list looking at wrong directory

Fix: Add get_default_hermes_root() to hermes_constants.py that detects
Docker/custom deployments (HERMES_HOME outside ~/.hermes) and returns
HERMES_HOME as the root. Also handles Docker profiles correctly
(<root>/profiles/<name> → root is grandparent).

Files changed:
- hermes_constants.py: new get_default_hermes_root()
- hermes_cli/profiles.py: _get_default_hermes_home() delegates to shared fn
- hermes_cli/main.py: _apply_profile_override() + _invalidate_update_cache()
- hermes_cli/gateway.py: _profile_suffix() + _profile_arg()
- Tests: 12 new tests covering Docker scenarios

tests/hermes_cli/test_update_check.py

@@ -1,6 +1,7 @@
 """Tests for the update check mechanism in hermes_cli.banner."""
 
 import json
+import os
 import threading
 import time
 from pathlib import Path
@@ -144,7 +145,8 @@ def test_invalidate_update_cache_clears_all_profiles(tmp_path):
         p.mkdir(parents=True)
         (p / ".update_check").write_text('{"ts":1,"behind":50}')
 
-    with patch.object(Path, "home", return_value=tmp_path):
+    with patch.object(Path, "home", return_value=tmp_path), \
+         patch.dict(os.environ, {"HERMES_HOME": str(default_home)}):
         _invalidate_update_cache()
 
     # All three caches should be gone
@@ -161,7 +163,8 @@ def test_invalidate_update_cache_no_profiles_dir(tmp_path):
     default_home.mkdir()
     (default_home / ".update_check").write_text('{"ts":1,"behind":5}')
 
-    with patch.object(Path, "home", return_value=tmp_path):
+    with patch.object(Path, "home", return_value=tmp_path), \
+         patch.dict(os.environ, {"HERMES_HOME": str(default_home)}):
         _invalidate_update_cache()
 
     assert not (default_home / ".update_check").exists()