igdb search + capped http reads: native fulltext, full-page fetch

search_games used `where name ~ "<q>"*`: prefix-only, diacritic- and
word-order-sensitive -- "MARVEL Tōkon" found nothing though IGDB has
it. Switch to IGDB's native `search` clause (relevance-ranked,
diacritic-insensitive).

fetch_url and image downloads read bodies with content.read(n), which
returns only the first buffered chunk (~7 KB): pages collapsed to
their <title>. httpread.read_capped collects chunks up to the byte
cap; image downloads read limit+1 so over-limit files are still
rejected instead of cached truncated (IMG-10).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_spec_imgcache.py

@@ -45,6 +45,45 @@ class TestIngest(unittest.TestCase):
             self.assertIsNone(cache.ingest_bytes(PNG, "chat", "alice", "1"))
 
 
+class TestOversizedDownloadRejected(unittest.IsolatedAsyncioTestCase):
+    async def test_download_stays_over_limit_and_is_rejected(self):
+        """IMG-10: an over-limit download must be rejected, not cached truncated."""
+        with tempfile.TemporaryDirectory() as tmp:
+            _, cache = make_cache(tmp, {"image-max-bytes": 32})
+
+            class FakeContent:
+                @staticmethod
+                async def iter_chunked(size):
+                    yield PNG  # 72 bytes > 32
+
+            class FakeResp:
+                content = FakeContent()
+
+                async def __aenter__(self):
+                    return self
+
+                async def __aexit__(self, *a):
+                    return False
+
+                def raise_for_status(self):
+                    pass
+
+            class FakeSession:
+                def get(self, url):
+                    return FakeResp()
+
+                async def __aenter__(self):
+                    return self
+
+                async def __aexit__(self, *a):
+                    return False
+
+            with patch("fjerkroa_bot.images.aiohttp.ClientSession", return_value=FakeSession()):
+                data = await cache._download("http://x.com/big.png")
+                self.assertEqual(len(data), 33)  # limit + 1, not silently capped to limit
+                self.assertIsNone(await cache.ingest_url("http://x.com/big.png", "chat", "alice", "1"))
+
+
 class TestVisionDataUrls(OpsBase):
     async def test_attachment_becomes_data_url(self):
         """IMG-11: the model sees a data: URL, never the CDN link."""