feat: initial commit for starlane-router (FastAPI + Gradient)

app/router.py

@@ -0,0 +1,21 @@
+from typing import Optional
+from .config import get_route_keywords
+
+
+def decide_route(*, message: str, explicit_hint: Optional[str] = None) -> str:
+    if explicit_hint:
+        hint = explicit_hint.strip().lower()
+        if hint in {"gradient", "local"}:
+            return hint
+
+    text = (message or "").strip().lower()
+
+    # Simple heuristic: if message is long or has keywords, use gradient
+    if len(text) > 120:
+        return "gradient"
+
+    for kw in get_route_keywords():
+        if kw in text:
+            return "gradient"
+
+    return "local"