Add unit tests for venvManager/condaEnvManager create & remove orchestration #1624

The createEnvironment / removeEnvironment orchestration in src/managers/builtin/venvManager.ts and src/managers/conda/condaEnvManager.ts has no unit-level coverage of the create/remove lifecycle. venvUtils.removeVenv and several condaEnvManager sub-behaviors (setEvents, setGlobal, findEnvironmentByPath) are unit-tested, but the manager methods that tie discovery, creation, caching, and change events together are only covered via integration tests.