refactor(lab): restore canonical RAV004 replay

src/k1link/web/session_api.py

@@ -835,11 +835,11 @@ def build_session_router(
         session_id: str,
         generation: Annotated[str, Query(min_length=64, max_length=64)],
         time_ns: Annotated[int, Query(ge=0, le=MAX_SAFE_INTEGER)],
-        profile: Literal["source-paced-ground-v2"],
+        profile: Literal["source-paced-ground-v3"],
     ) -> JSONResponse:
         """Serve one body-frame sample for the canonical recorded-LAB clock.
 
-        The camera timeline owns playback.  Spatial evidence is sampled from
+        The camera media clock owns playback. Spatial evidence is sampled from
         the same immutable recording instead of starting a second Rerun clock.
         """