Prevent no_std websocket request-id panic when id is missing

[Copilot]

High Level Overview of Change

no_std websocket requests could panic when id was omitted: set_request_id hit unimplemented!() and request_impl unwrapped id. This change converts that path to explicit error handling and removes the panic source.

• XRPLClient::set_request_id no_std behavior

  • Removed the unimplemented!() branch for not(feature = "std").
  • In no_std, missing id is now left unchanged instead of panicking.

• No_std websocket request path

  • Replaced unwrap() on request.get_common_fields().id with a checked path returning XRPLWebSocketException::InvalidMessage.

• Regression coverage

  • Added a no_std unit test verifying set_request_id does not panic and does not synthesize an ID.

Context of Change

The bug was in the no_std websocket request flow: request IDs are auto-generated only in std, but no_std code still assumed an ID exists and panicked at runtime if callers did not pre-set one. This update makes no_std behavior deterministic and non-panicking by surfacing a normal client error.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (You added tests for code that already exists, or your new feature included in this PR)
• Documentation Updates
• Release

Before / After

Before (no_std):

self.set_request_id(&mut request);
let request_id = request.get_common_fields().id.as_ref().unwrap();

After (no_std):

self.set_request_id(&mut request);
let request_id = request
    .get_common_fields()
    .id
    .as_ref()
    .ok_or(XRPLWebSocketException::InvalidMessage)?;

Test Plan

Added unit coverage for no_std request ID handling in src/asynch/clients/client.rs:

• set_request_id_no_std_does_not_panic_or_generate_id