Fix sample generation for nested @bodyRoot parameters

[JialinHuang803]

Problem

When an operation has a @bodyRoot property nested inside a wrapper model (e.g., body: { @bodyRoot stopParameters: StopParameters }), the generated sample code in samples-dev/ was missing the required body parameter entirely.

Root Cause

In emitSamples.ts and exampleValueHelpers.ts, prepareExampleParameters uses bodyParam.name ("stopParameters") as the example parameter name. However, the function signature parameter is the wrapper "body". When the reorder logic does paramValueMap.get("body"), it returns undefined because the map key is "stopParameters", causing the body parameter to be dropped.

Fix

Use bodyParam.methodParameterSegments to detect nested body parameters. When nested (single path with >1 segments):

1. Use the first segment's name as the parameter name (the method-level wrapper)
2. Wrap the example value with the intermediate property names to match the wrapper structure

Testing

• All 639 unit tests pass
• Regenerated networkGateway smoke test confirms sample now correctly includes the body parameter

Fixes #3968