What does this PR do?

In containers where the runtime user is non-root and the image `WORKDIR` (typically `/opt/hermes` under the Dockerfile) is owned by root, `Path.home()` resolves to a directory the process cannot write to. The gateway lock directory then fails to materialize:

```
PermissionError: [Errno 13] Permission denied: '/opt/hermes/.local'
File "/opt/hermes/gateway/status.py", line 471, in acquire_scoped_lock
lock_path.parent.mkdir(parents=True, exist_ok=True)
```

The reproduction in the issue was a podman quadlet with `UserNS=keep-id` + `User=%U:%G`, where podman runs the container under the host UID without adjusting the container-side `/etc/passwd` entry, so `$HOME` ends up at the `WORKDIR` rather than the `hermes` user's home.

This PR adds a fallback step to `_get_lock_dir()`:

`HERMES_HOME` is the documented runtime data root and is always intended to be writable (that's where the container volume mounts). It's the natural backstop for state files when `$HOME` is locked down.

The probe result is memoized in `_resolve_default_lock_dir` so repeated `acquire_scoped_lock` calls don't re-issue `mkdir` syscalls.

Related Issue

Fixes #16550

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• `gateway/status.py` — split `_get_lock_dir()`: env-driven branches stay un-cached for testability; the default-path probe lives in `_resolve_default_lock_dir` with `functools.lru_cache(maxsize=1)`. Probe failures fall back to `HERMES_HOME / "gateway-locks"` and emit a warning naming both `HERMES_GATEWAY_LOCK_DIR` and `XDG_STATE_HOME` as available overrides.
• `tests/gateway/test_status.py` — 5 new tests under `TestGetLockDir`: explicit override priority, XDG_STATE_HOME honor, default-path probe under writable HOME, fallback to HERMES_HOME under read-only HOME (the container scenario), and probe memoization.

How to Test

Reproduce the original failure (no fix):

```bash
docker run --rm -u 1000:1000 -e HERMES_HOME=/opt/data -v /tmp/data:/opt/data \
ghcr.io/nousresearch/hermes-agent gateway run

→ PermissionError: '/opt/hermes/.local'

```

After this PR, the same command falls back to `/opt/data/gateway-locks` and logs a warning.

Automated:
```bash
pytest tests/gateway/test_status.py

38 passed (5 new in TestGetLockDir)

```

Wider `tests/gateway/` suite: 1006 passed (4 pre-existing flaky failures in Discord / approve-deny tests unrelated to this change — verified by running them on `upstream/main` without this PR).

Notes

• Existing deployments with `~/.local/state` writable see no behavior change — the probe succeeds and returns the same path as before.
• Operators who want the lock directory in a specific location can still set `HERMES_GATEWAY_LOCK_DIR` or `XDG_STATE_HOME` explicitly; both short-circuit ahead of the probe.
• A complementary one-line fix in `docker/entrypoint.sh` (`export HERMES_GATEWAY_LOCK_DIR="$HERMES_HOME/gateway-locks"`) would make the explicit-override path active in the official image. Left out of this PR to keep the change purely fixing the runtime fallback; happy to follow up.