fix(executor): sanitize thought signatures in Gemini and Gemini Vertex executors (#5110)

Ensure all Gemini and Gemini Vertex execution and token count pathways invoke SanitizeGeminiRequestThoughtSignatures before dispatching upstream requests. This prevents raw non-Gemini (e.g. Claude CAIS) thought signatures from leaking to upstream Gemini endpoints while preserving valid native protobuf signatures and setting appropriate validator bypass sentinels for function calls.

Co-authored-by: W ARELIK <warelik@WARELIK-MB.local>