Add llm-gateway module: routing, failover below the tool-calling advisor, per-provider circuit breakers, dollar caps and token limits, tenant-keyed cache; real OpenAI and Anthropic models against a local fake

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01JXVi2GMQ7bR5EmbUFdDj7N

llm-gateway/src/main/java/com/ankurm/gateway/Routes.java

@@ -0,0 +1,22 @@
+package com.ankurm.gateway;
+
+import java.util.List;
+import java.util.Map;
+
+/** Maps a model hint to an ordered list of targets. An unknown hint is an error, not a default. */
+public final class Routes {
+
+    private final Map<String, List<Target>> table;
+
+    public Routes(Map<String, List<Target>> table) {
+        this.table = Map.copyOf(table);
+    }
+
+    public List<Target> get(String hint) {
+        List<Target> t = table.get(hint);
+        if (t == null) {
+            throw new UnknownHintException(hint, table.keySet());
+        }
+        return t;
+    }
+}