Description

Fixes a bug where XML tool parsing would occur even when Native Tool Calling (NTC) was enabled, causing confusion for the model.

The Problem

The issue occurred because the code only checked for the existence of this.assistantMessageParser to decide whether to parse XML content. However, the parser might exist due to:

1. Race conditions
2. Incomplete cleanup from previous tasks
3. Configuration switches mid-session

When a model (confused or otherwise) output XML-like text while in native mode, the presence of the parser would trigger XML parsing, even though the protocol was strictly native. This would cause the model to see parsed XML tools and continue using XML format instead of native tool calls.

The Fix

This PR introduces a robust check that verifies the current protocol before attempting any XML parsing:

1. Calculates shouldUseXmlParser once at the start of the API request loop (efficient)
2. Uses this flag in the streaming loop to guard XML parsing
3. Uses this flag in the finalization step

This ensures that even if the parser object exists in memory, it will NEVER be used if the current protocol is native.

Testing

• Verified with existing tests
• Added specific test case to cover the edge case where parser exists but protocol is native (verified locally then removed)
• All tests passed