feat(aux): use Portal /api/nous/recommended-models for auxiliary models

Wire the auxiliary client (compaction, vision, session search, web extract)
to the Nous Portal's curated recommended-models endpoint when running on
Nous Portal, with a TTL-cached fetch that mirrors how we pull /models for
pricing.

hermes_cli/models.py
  - fetch_nous_recommended_models(portal_base_url, force_refresh=False)
    10-minute TTL cache, keyed per portal URL (staging vs prod don't
    collide).  Public endpoint, no auth required.  Returns {} on any
    failure so callers always get a dict.
  - get_nous_recommended_aux_model(vision, free_tier=None, ...)
    Tier-aware pick from the payload:
      - Paid tier → paidRecommended{Vision,Compaction}Model, falling back
        to freeRecommended* when the paid field is null (common during
        staged rollouts of new paid models).
      - Free tier → freeRecommended* only, never leaks paid models.
    When free_tier is None, auto-detects via the existing
    check_nous_free_tier() helper (already cached 3 min against
    /api/oauth/account).  Detection errors default to paid so we never
    silently downgrade a paying user.

agent/auxiliary_client.py — _try_nous()
  - Replaces the hardcoded xiaomi/mimo free-tier branch with a single call
    to get_nous_recommended_aux_model(vision=vision).
  - Falls back to _NOUS_MODEL (google/gemini-3-flash-preview) when the
    Portal is unreachable or returns a null recommendation.
  - The Portal is now the source of truth for aux model selection; the
    xiaomi allowlist we used to carry is effectively dead.

Tests (15 new)
  - tests/hermes_cli/test_models.py::TestNousRecommendedModels
    Fetch caching, per-portal keying, network failure, force_refresh;
    paid-prefers-paid, paid-falls-to-free, free-never-leaks-paid,
    auto-detect, detection-error → paid default, null/blank modelName
    handling.
  - tests/agent/test_auxiliary_client.py::TestNousAuxiliaryRefresh
    _try_nous honors Portal recommendation for text + vision, falls
    back to google/gemini-3-flash-preview on None or exception.

Behavior won't visibly change today — both tier recommendations currently
point at google/gemini-3-flash-preview — but the moment the Portal ships
a better paid recommendation, subscribers pick it up within 10 minutes
without a Hermes release.

hermes_cli/models.py

@@ -513,6 +513,157 @@ def check_nous_free_tier() -> bool:
         return False  # default to paid on error — don't block users
 
 
+# ---------------------------------------------------------------------------
+# Nous Portal recommended models
+#
+# The Portal publishes a curated list of suggested models (separated into
+# paid and free tiers) plus dedicated recommendations for compaction (text
+# summarisation / auxiliary) and vision tasks. We fetch it once per process
+# with a TTL cache so callers can ask "what's the best aux model right now?"
+# without hitting the network on every lookup.
+#
+# Shape of the response (fields we care about):
+#   {
+#     "paidRecommendedModels":     [ {modelName, ...}, ... ],
+#     "freeRecommendedModels":     [ {modelName, ...}, ... ],
+#     "paidRecommendedCompactionModel":  {modelName, ...} | null,
+#     "paidRecommendedVisionModel":      {modelName, ...} | null,
+#     "freeRecommendedCompactionModel":  {modelName, ...} | null,
+#     "freeRecommendedVisionModel":      {modelName, ...} | null,
+#   }
+# ---------------------------------------------------------------------------
+
+NOUS_RECOMMENDED_MODELS_PATH = "/api/nous/recommended-models"
+_NOUS_RECOMMENDED_CACHE_TTL: int = 600  # seconds (10 minutes)
+# (result_dict, timestamp) keyed by portal_base_url so staging vs prod don't collide.
+_nous_recommended_cache: dict[str, tuple[dict[str, Any], float]] = {}
+
+
+def fetch_nous_recommended_models(
+    portal_base_url: str = "",
+    timeout: float = 5.0,
+    *,
+    force_refresh: bool = False,
+) -> dict[str, Any]:
+    """Fetch the Nous Portal's curated recommended-models payload.
+
+    Hits ``<portal>/api/nous/recommended-models``. The endpoint is public —
+    no auth is required. Results are cached per portal URL for
+    ``_NOUS_RECOMMENDED_CACHE_TTL`` seconds; pass ``force_refresh=True`` to
+    bypass the cache.
+
+    Returns the parsed JSON dict on success, or ``{}`` on any failure
+    (network, parse, non-2xx). Callers must treat missing/null fields as
+    "no recommendation" and fall back to their own default.
+    """
+    base = (portal_base_url or "https://portal.nousresearch.com").rstrip("/")
+    now = time.monotonic()
+    cached = _nous_recommended_cache.get(base)
+    if not force_refresh and cached is not None:
+        payload, cached_at = cached
+        if now - cached_at < _NOUS_RECOMMENDED_CACHE_TTL:
+            return payload
+
+    url = f"{base}{NOUS_RECOMMENDED_MODELS_PATH}"
+    try:
+        req = urllib.request.Request(
+            url,
+            headers={"Accept": "application/json"},
+        )
+        with urllib.request.urlopen(req, timeout=timeout) as resp:
+            data = json.loads(resp.read().decode())
+        if not isinstance(data, dict):
+            data = {}
+    except Exception:
+        data = {}
+
+    _nous_recommended_cache[base] = (data, now)
+    return data
+
+
+def _resolve_nous_portal_url() -> str:
+    """Best-effort lookup of the Portal base URL the user is authed against."""
+    try:
+        from hermes_cli.auth import (
+            DEFAULT_NOUS_PORTAL_URL,
+            get_provider_auth_state,
+        )
+        state = get_provider_auth_state("nous") or {}
+        portal = str(state.get("portal_base_url") or "").strip()
+        if portal:
+            return portal.rstrip("/")
+        return str(DEFAULT_NOUS_PORTAL_URL).rstrip("/")
+    except Exception:
+        return "https://portal.nousresearch.com"
+
+
+def _extract_model_name(entry: Any) -> Optional[str]:
+    """Pull the ``modelName`` field from a recommended-model entry, else None."""
+    if not isinstance(entry, dict):
+        return None
+    model_name = entry.get("modelName")
+    if isinstance(model_name, str) and model_name.strip():
+        return model_name.strip()
+    return None
+
+
+def get_nous_recommended_aux_model(
+    *,
+    vision: bool = False,
+    free_tier: Optional[bool] = None,
+    portal_base_url: str = "",
+    force_refresh: bool = False,
+) -> Optional[str]:
+    """Return the Portal's recommended model name for an auxiliary task.
+
+    Picks the best field from the Portal's recommended-models payload:
+
+    * ``vision=True``  → ``paidRecommendedVisionModel``  (paid tier) or
+                         ``freeRecommendedVisionModel``  (free tier)
+    * ``vision=False`` → ``paidRecommendedCompactionModel`` or
+                         ``freeRecommendedCompactionModel``
+
+    When ``free_tier`` is ``None`` (default) the user's tier is auto-detected
+    via :func:`check_nous_free_tier`. Pass an explicit bool to bypass the
+    detection — useful for tests or when the caller already knows the tier.
+
+    For paid-tier users we prefer the paid recommendation but gracefully fall
+    back to the free recommendation if the Portal returned ``null`` for the
+    paid field (common during the staged rollout of new paid models).
+
+    Returns ``None`` when every candidate is missing, null, or the fetch
+    fails — callers should fall back to their own default (currently
+    ``google/gemini-3-flash-preview``).
+    """
+    base = portal_base_url or _resolve_nous_portal_url()
+    payload = fetch_nous_recommended_models(base, force_refresh=force_refresh)
+    if not payload:
+        return None
+
+    if free_tier is None:
+        try:
+            free_tier = check_nous_free_tier()
+        except Exception:
+            # On any detection error, assume paid — paid users see both fields
+            # anyway so this is a safe default that maximises model quality.
+            free_tier = False
+
+    if vision:
+        paid_key, free_key = "paidRecommendedVisionModel", "freeRecommendedVisionModel"
+    else:
+        paid_key, free_key = "paidRecommendedCompactionModel", "freeRecommendedCompactionModel"
+
+    # Preference order:
+    #   free tier  → free only
+    #   paid tier  → paid, then free (if paid field is null)
+    candidates = [free_key] if free_tier else [paid_key, free_key]
+    for key in candidates:
+        name = _extract_model_name(payload.get(key))
+        if name:
+            return name
+    return None
+
+
 # ---------------------------------------------------------------------------
 # Canonical provider list — single source of truth for provider identity.
 # Every code path that lists, displays, or iterates providers derives from