WebSiteManagementClient.web_apps.list_by_resource_group (and az webapp list) silently under-reports results on resource groups with 100+ App Services

Package Name: azure-mgmt-web
Package Version: 11.0.0
Operating System: Windows 11
Python Version: 3.13

**Describe the bug**
WebSiteManagementClient.web_apps.list_by_resource_group() silently under-reports results on a resource group with 100+ App Services, returning only 32 of 101 existing resources with no error, exception, or indication that results were truncated. The Azure CLI command az webapp list (against the same resource group, same identity) exhibits the identical behavior, suggesting both share the same underlying listing logic. Azure Resource Graph and az resource list, queried against the same resource group, correctly return all 101.

**To Reproduce**
Steps to reproduce the behavior:
1. az resource list -g --resource-type Microsoft.Web/sites --query "length(@)"
2. az resource list -g --resource-type Microsoft.Web/sites --query "[].kind" -o tsv | sort | uniq - c - returns all the resources count
Code which is not working:
from azure.identity import DefaultAzureCredential
from azure.mgmt.web import WebSiteManagementClient

credential = DefaultAzureCredential()
client = WebSiteManagementClient(credential, subscription_id="")
apps = list(client.web_apps.list_by_resource_group(""))
print(len(apps))

**Expected behavior**
list_by_resource_group() should return all App Services in the resource group, matching the count returned by Azure Resource Graph (Resources | where type =~ 'microsoft.web/sites' | where resourceGroup =~ 'bic-web-apps-rg') and az resource list --resource-type Microsoft.Web/sites, both of which correctly.

**Additional context**
Ruled out RBAC/permission scoping: same identity used for the CLI, the SDK, the Azure portal, and Resource Graph
Ruled out kind-based filtering (e.g. Function Apps or Logic Apps Standard being excluded from web-app-specific listings):
Workaround in use: querying Azure Resource Graph directly (bypassing list_by_resource_group entirely) returns the correct, complete count.
Suspected root cause: a pagination/continuation-token handling issue specific to the Microsoft.Web/sites list endpoint, shared by both the CLI and the Python SDK.
If this doesn't reproduce on a freshly created test resource group, it may be specific to something about our subscription or data rather than a universal SDK bug —
happy to open an Azure Support case and share the x-ms-correlation-request-id / x-ms-request-id from a failing call (visible via az webapp list --debug) so the request can be traced server-side without needing access to our environment.

Comienza reproduciendo la discrepancia con WebSiteManagementClient.web_apps.list_by_resource_group() y az webapp list, y luego compara sus recuentos con az resource list para el mismo grupo de recursos. Investiga el comportamiento de listado y paginación de Microsoft.Web/sites; se considera completado cuando tanto el SDK como la CLI devuelven todos los App Services existentes sin truncamiento silencioso.

Escrito por el modelo de indexación a partir del texto del issue.