test: add baseline gateway regression suites

Add focused unittest coverage for auth/concurrency, schema normalization, and session-cache tooling behavior, and ignore local .gitnexus index artifacts.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_session_cache_tooling.py

@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+import unittest
+
+from app.session_cache import SessionCache, hash_user_context
+
+
+class SessionCacheToolingTests(unittest.IsolatedAsyncioTestCase):
+    def test_hash_user_context_ignores_assistant_and_tool(self) -> None:
+        base = [
+            {"role": "system", "content": "S"},
+            {"role": "user", "content": "U"},
+        ]
+        with_extra = base + [
+            {"role": "assistant", "content": "A1"},
+            {"role": "tool", "content": "T1"},
+        ]
+        self.assertEqual(hash_user_context(base), hash_user_context(with_extra))
+
+    def test_build_key_changes_with_tool_config(self) -> None:
+        cache = SessionCache(max_entries=8, ttl_sec=60)
+        msgs = [{"role": "user", "content": "hi"}]
+        key1 = cache.build_key("k", msgs, tool_config={"a": 1, "b": 2})
+        key2 = cache.build_key("k", msgs, tool_config={"b": 2, "a": 1})
+        key3 = cache.build_key("k", msgs, tool_config={"a": 1})
+        self.assertEqual(key1, key2)
+        self.assertNotEqual(key1, key3)
+
+    async def test_lru_evicts_oldest(self) -> None:
+        cache = SessionCache(max_entries=2, ttl_sec=600)
+        await cache.put("k1", "s1")
+        await cache.put("k2", "s2")
+        await cache.put("k3", "s3")
+        self.assertIsNone(await cache.get("k1"))
+        self.assertEqual(cache.evict_total, 1)
+
+    async def test_ttl_expiry_increments_expire_counter(self) -> None:
+        cache = SessionCache(max_entries=4, ttl_sec=0.001)
+        await cache.put("k1", "s1")
+        await __import__("asyncio").sleep(0.01)
+        self.assertIsNone(await cache.get("k1"))
+        self.assertEqual(cache.expire_total, 1)
+
+
+if __name__ == "__main__":
+    unittest.main()