_resolve_container_task_id always returned "default", so _active_environments
shared a single SSHEnvironment across all WebUI sessions. When a user switched
from profile A (ssh_host=10.0.0.1) to profile B (ssh_host=10.0.0.2), the new
session found _active_environments["default"] already set to A's SSHEnvironment
and reused it — silently running every command on the wrong remote host.
Fix: when HERMES_SESSION_KEY is present (set per-session by the WebUI streaming
layer and per-message by the gateway via contextvars), return "session:<key>"
as the cache key instead of "default". Each session now owns its own slot in
_active_environments and always creates an environment from its own profile's
TERMINAL_SSH_HOST / TERMINAL_ENV config.
Behaviour unchanged in CLI mode (no HERMES_SESSION_KEY → still "default").
RL/benchmark task overrides (register_task_env_overrides) are unaffected.
Subagent task_ids inside a WebUI session collapse to "session:<key>" so they
continue to share the parent session's container.
Five new regression tests added to test_shared_container_task_id.py.
carryzuo00
a270c4adea