test: start test_raw_frameset from empty shared-encoding caches

The previous commit's shared-JPEG test failed when run with the others:
the module-level caches kept entries numbered 1 from earlier tests' fake
cameras (each numbers its framesets from 1). The service is not affected:
a cache hit also requires the same frame object. The fixture now clears
the caches.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_raw_frameset.py

@@ -42,6 +42,9 @@ def client():
     cam = RealSenseD435()
     open_fake_camera(cam, FakePipeline(fps=30), FakeAlign(delay_s=0.0))
     _identity_calibration(cam)
+    # Each fake camera numbers its framesets from 1: start from empty shared-encoding caches.
+    routes._encoded_colors.clear()
+    routes._encoded_raws.clear()
     routes.set_camera(cam)
     websocket.set_camera(cam)
     yield TestClient(app)