feat: model registry Phase 2 — cloud provider UI (Anthropic + Google)

Adds cloud provider management to /settings/models:
- Google Accounts section: add/remove Gemini API keys with labels
- Add Model form: provider tabs (Local / Google / Anthropic) with
  catalog dropdowns that auto-fill label and context_k
- Provider badges on model rows (Anthropic / Google / Local)
- /settings/local now redirects to /settings/models (canonical URL)
- save_cloud_model() in model_registry for Anthropic/Google entries
- Distill role migration restored in _migrate_from_local_llm
- Test fixes: version assertions updated to V2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/model_registry.py

@@ -296,6 +296,8 @@ def _migrate_from_local_llm(username: str, path: Path) -> dict:
     active_id = old.get("active_model_id")
     if active_id and any(m["id"] == active_id for m in data["models"]):
         data["roles"]["chat"] = {"primary": active_id}
+        if settings.distill_backend_mid == "local":
+            data["roles"]["distill"] = {"primary": active_id}
 
     # Migrate Gemini key from auth.json
     data = _migrate_v1_to_v2(username, {"version": 1, **data})
@@ -613,6 +615,52 @@ def save_model(username: str, model_id: str | None, host_id: str,
     return model_id
 
 
+def save_cloud_model(username: str, model_id: str | None,
+                     provider: str, model_name: str, label: str,
+                     account_id: str | None = None,
+                     credential_id: str | None = None,
+                     context_k: int = 0,
+                     tags: list[str] | None = None) -> str:
+    """
+    Create or update an Anthropic or Google model entry. Returns the model ID.
+
+    provider: "anthropic" | "google"
+    account_id:    Google only — references providers.google.accounts[].id
+    credential_id: Anthropic only — e.g. "cli"
+    """
+    _TYPE = {"google": "gemini_api", "anthropic": "claude_cli"}
+    entry_type = _TYPE.get(provider, "gemini_api")
+    data = _load(username)
+    tags = tags or []
+
+    entry: dict = {
+        "type":       entry_type,
+        "label":      label.strip() or model_name.strip(),
+        "model_name": model_name.strip(),
+        "provider":   provider,
+        "context_k":  context_k,
+        "tags":       tags,
+    }
+    if account_id:
+        entry["account_id"] = account_id
+    if credential_id:
+        entry["credential_id"] = credential_id
+
+    if model_id:
+        for m in data["models"]:
+            if m["id"] == model_id:
+                m.update(entry)
+                _save(username, data)
+                return model_id
+        model_id = None
+
+    model_id = secrets.token_hex(4)
+    entry["id"] = model_id
+    data["models"].append(entry)
+    _save(username, data)
+    return model_id
+
+
 def remove_model(username: str, model_id: str) -> bool:
     """Remove a model and clear any role assignments pointing to it."""
     data = _load(username)