deps: require vgi-rpc 0.31.0

The call/cursor token split, StreamStateCodec support on Stream, and the
shared waitress tuning helper all live there; this repo's code does not
import cleanly against 0.30.0.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: rustyconover

pyproject.toml

@@ -40,7 +40,7 @@ dependencies = [
     "pyarrow",
     "typer>=0.9",
     "platformdirs",
-    "vgi-rpc>=0.28.3",
+    "vgi-rpc>=0.31.0",
     "httpx>=0.24",
 ]