fix: resolve pyright type errors in test_streamable_http.py

- Add generic type parameters to ServerRequestContext annotation
- Replace isinstance(Request) checks with None checks since type is already narrowed

Fixes pre-commit CI failure in weekly dependency update PR

Author: goingforstudying-ctrl

tests/shared/test_streamable_http.py

@@ -1489,14 +1489,14 @@ async def _handle_context_list_tools(  # pragma: no cover
 
 
 async def _handle_context_call_tool(  # pragma: no cover
-    ctx: ServerRequestContext, params: CallToolRequestParams
+    ctx: ServerRequestContext[Any, Request[Any]], params: CallToolRequestParams
 ) -> CallToolResult:
     name = params.name
     args = params.arguments or {}
 
     if name == "echo_headers":
         headers_info: dict[str, Any] = {}
-        if ctx.request and isinstance(ctx.request, Request):
+        if ctx.request is not None:
             headers_info = dict(ctx.request.headers)
         return CallToolResult(content=[TextContent(type="text", text=json.dumps(headers_info))])
 
@@ -1507,7 +1507,7 @@ async def _handle_context_call_tool(  # pragma: no cover
             "method": None,
             "path": None,
         }
-        if ctx.request and isinstance(ctx.request, Request):
+        if ctx.request is not None:
             request = ctx.request
             context_data["headers"] = dict(request.headers)
             context_data["method"] = request.method