Operations in client.tsp should not raise arm-resource-operation / documentation-required warnings

## Description

When an operation defined in a `client.tsp` file is used only as the **source of an `@@override`** (i.e. it is not a real service operation but a client-shaping helper), it still triggers linter warnings that require manual suppressions.

For example, an operation must carry two suppressions purely because it is an override source:

```tsp
// overrides: subscriptionId should be method level
#suppress "@azure-tools/typespec-azure-resource-manager/arm-resource-operation" "FIXME: Update justification"
#suppress "@azure-tools/typespec-azure-core/documentation-required" "FIXME: Update justification"
op quotaRequestStatusGet(
...ApiVersionParameter,
...SubscriptionIdParameter,
...
): ArmResponse | ExceptionResponse;
@@override(QuotaRequestStatus.get, quotaRequestStatusGet);
@@clientLocation(
quotaRequestStatusGet::parameters.subscriptionId,
quotaRequestStatusGet
);
```

Without the two `#suppress` lines, compilation raises:
- `@azure-tools/typespec-azure-resource-manager/arm-resource-operation`
- `@azure-tools/typespec-azure-core/documentation-required`

## Expected behavior

An operation that is only used as an `@@override` source should not raise these warnings. It is a client customization construct, not a service operation, so ARM resource-operation and documentation-required rules should not apply to it.

## Actual behavior

The operation is linted like a normal service operation, forcing spec authors to add boilerplate `#suppress` directives (currently generated with placeholder `FIXME` justifications by the conversion tooling).

Start by locating the implementations of the arm-resource-operation and documentation-required rules, then inspect how an operation used only as an @@override source is identified. Reproduce the client.tsp example without its suppressions and verify that compilation no longer emits either warning, while normal service operations retain both checks.

Written by the indexing model from the issue text.