fix(auth): mirror Nous OAuth credentials to providers.nous on CLI login

`hermes auth add nous --type oauth` only wrote credential_pool.nous,
leaving providers.nous empty. When the Nous agent_key's 24h TTL expired,
run_agent.py's 401-recovery path called resolve_nous_runtime_credentials
(which reads providers.nous), got AuthError "Hermes is not logged into
Nous Portal", caught it as logger.debug (suppressed at INFO level), and
the agent died with "Non-retryable client error" — no signal to the
user that recovery even tried.

Introduce persist_nous_credentials() as the single source of truth for
Nous device-code login persistence. Both auth_commands (CLI) and
web_server (dashboard) now route through it, so pool and providers
stay in sync at write time.

Why: CLI-provisioned profiles couldn't recover from agent_key expiry,
producing silent daily outages 24h after first login. PR #6856/#6869
addressed adjacent issues but assumed providers.nous was populated;
this one wasn't being written.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

hermes_cli/web_server.py

@@ -1444,38 +1444,13 @@ def _nous_poller(session_id: str) -> None:
             auth_state, min_key_ttl_seconds=300, timeout_seconds=15.0,
             force_refresh=False, force_mint=True,
         )
-        # Save into credential pool same as auth_commands.py does
-        from agent.credential_pool import (
-            PooledCredential,
-            load_pool,
-            AUTH_TYPE_OAUTH,
-            SOURCE_MANUAL,
+        from agent.credential_pool import SOURCE_MANUAL
+        from hermes_cli.auth import persist_nous_credentials
+        persist_nous_credentials(
+            full_state,
+            label="dashboard device_code",
+            source=f"{SOURCE_MANUAL}:dashboard_device_code",
         )
-        pool = load_pool("nous")
-        entry = PooledCredential.from_dict("nous", {
-            **full_state,
-            "label": "dashboard device_code",
-            "auth_type": AUTH_TYPE_OAUTH,
-            "source": f"{SOURCE_MANUAL}:dashboard_device_code",
-            "base_url": full_state.get("inference_base_url"),
-        })
-        pool.add_entry(entry)
-        # Also persist to auth store so get_nous_auth_status() sees it
-        # (matches what _login_nous in auth.py does for the CLI flow).
-        try:
-            from hermes_cli.auth import (
-                _load_auth_store, _save_provider_state, _save_auth_store,
-                _auth_store_lock,
-            )
-            with _auth_store_lock():
-                auth_store = _load_auth_store()
-                _save_provider_state(auth_store, "nous", full_state)
-                _save_auth_store(auth_store)
-        except Exception as store_exc:
-            _log.warning(
-                "oauth/device: credential pool saved but auth store write failed "
-                "(session=%s): %s", session_id, store_exc,
-            )
         with _oauth_sessions_lock:
             sess["status"] = "approved"
         _log.info("oauth/device: nous login completed (session=%s)", session_id)