* feat(models): add support for Gemini 3.1 and custom tool models
* test(routing): fix classifier and numerical classifier strategy tests
* test(routing): add Gemini 3.1 tests for classifier strategy
* fix(models): correctly filter active Gemini 3.1 models
* fix(routing): ensure useCustomToolModel is only true when Gemini 3.1 is enabled
* fix(test-utils): prevent double newline in lastFrame() on Windows
* fix(test-utils): surgically fix double newline in lastFrame() on Windows
* use custom_tools_model string for api key only
* fix(ui): correct useCustomToolModel logic and update tests
* fix(ui): correct useCustomToolModel logic in StatsDisplay
* fix(routing): ensure test models are active and sync useCustomToolModel logic
* feat(core,ui): support Gemini 3.1 Pro Preview and active model filtering
* fix(core,ui): use optional chaining for config methods to support mocks
* fix(core): clear stale authType in refreshAuth to avoid incorrect model resolution
* do not show gemini 3.1 model when users do not have access to gemini 3.1 in stats
Sehoon Shon