fix: minimize dependency upgrade compatibility changes

Remove cache-only workflow edits and preserve the request forwarder's existing error behavior while satisfying the upgraded Python type checker.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

.github/workflows/codegen-check.yml

@@ -37,7 +37,6 @@ jobs:
       - uses: actions/setup-go@v7
         with:
           go-version: '1.25'
-          cache-dependency-path: "go/go.sum"
 
       # Rust generator runs `cargo fmt` on the output, so we need a toolchain with rustfmt.
       - name: Install Rust toolchain

.github/workflows/copilot-setup-steps.yml

@@ -55,7 +55,6 @@ jobs:
         uses: actions/setup-go@v7
         with:
           go-version: "1.25"
-          cache-dependency-path: "go/go.sum"
 
       # Setup .NET (for .NET SDK)
       - name: Set up .NET

.github/workflows/go-sdk-tests.yml

@@ -33,7 +33,6 @@ jobs:
       - uses: actions/setup-go@v7
         with:
           go-version: "1.25"
-          cache-dependency-path: "go/go.sum"
 
       - name: Run go fmt
         if: runner.os == 'Linux'

.github/workflows/update-copilot-dependency.yml

@@ -35,7 +35,6 @@ jobs:
       - uses: actions/setup-go@v7
         with:
           go-version: "1.25"
-          cache-dependency-path: "go/go.sum"
 
       - uses: actions/setup-dotnet@v6
         with:

python/copilot/copilot_request_handler.py

@@ -25,7 +25,7 @@
 import base64
 from collections.abc import AsyncIterator, Callable
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, cast
 
 from .generated.rpc import (
     LlmInferenceHTTPRequestChunkRequest,
@@ -207,9 +207,7 @@ async def open(self) -> None:
         self._receive_task = asyncio.create_task(self._receive_loop())
 
     async def _receive_loop(self) -> None:
-        upstream = self._upstream
-        if upstream is None:
-            return
+        upstream = cast(Any, self._upstream)
         try:
             async for message in upstream:
                 await self.send_response_message(message)