Claude models accessed through Google Cloud Code Assist API require
explicit id fields in both functionCall and functionResponse parts.
Without these IDs, the API returns 'tool_use.id: Field required' error.
Add requiresToolCallId() helper to centralize the Claude model detection
and include IDs in both tool call and tool result message conversions.
* Avoid cross-provider thought signatures
* Fix Google thought signature replay
Filter thought signatures to same provider with base64 validation and rename the transform helper for clarity.
Danila Poyarkov