Add OpenRouter backup key failover

src/humeo/env.py

@@ -59,15 +59,42 @@ def resolve_gemini_api_key() -> str:
     )
 
 
-def resolve_openrouter_api_key() -> str:
-    """Return the OpenRouter API key, or raise if missing."""
-    bootstrap_env()
-    val = (os.environ.get("OPENROUTER_API_KEY") or "").strip()
-    if val:
-        return val
-    raise ValueError(
-        "Set OPENROUTER_API_KEY to use OpenRouter as the backend for the Gemini stages. "
-        "See docs/ENVIRONMENT.md."
+def resolve_openrouter_api_key() -> str:
+    """Return the OpenRouter API key, or raise if missing."""
+    return resolve_openrouter_api_keys()[0]
+
+
+def resolve_openrouter_api_keys() -> list[str]:
+    """Return OpenRouter API keys in failover order, or raise if missing.
+
+    ``OPENROUTER_API_KEY`` remains the primary key. Optional backups can be
+    supplied with ``OPENROUTER_API_KEY_BACKUP``, ``OPENROUTER_API_KEY_2``, or
+    a comma/newline-separated ``OPENROUTER_API_KEYS`` value.
+    """
+    bootstrap_env()
+    keys: list[str] = []
+    for env_name in (
+        "OPENROUTER_API_KEY",
+        "OPENROUTER_API_KEY_BACKUP",
+        "OPENROUTER_API_KEY_2",
+    ):
+        val = (os.environ.get(env_name) or "").strip()
+        if val:
+            keys.append(val)
+
+    extra = (os.environ.get("OPENROUTER_API_KEYS") or "").strip()
+    if extra:
+        for item in extra.replace("\n", ",").split(","):
+            val = item.strip()
+            if val:
+                keys.append(val)
+
+    deduped = list(dict.fromkeys(keys))
+    if deduped:
+        return deduped
+    raise ValueError(
+        "Set OPENROUTER_API_KEY to use OpenRouter as the backend for the Gemini stages. "
+        "See docs/ENVIRONMENT.md."
     )
 
 
@@ -84,8 +111,16 @@ def current_llm_provider() -> LLMProvider | None:
         return "google"
     if (os.environ.get("GEMINI_API_KEY") or "").strip():
         return "google"
-    if (os.environ.get("OPENROUTER_API_KEY") or "").strip():
-        return "openrouter"
+    if any(
+        (os.environ.get(name) or "").strip()
+        for name in (
+            "OPENROUTER_API_KEY",
+            "OPENROUTER_API_KEY_BACKUP",
+            "OPENROUTER_API_KEY_2",
+            "OPENROUTER_API_KEYS",
+        )
+    ):
+        return "openrouter"
     return None