feat: Enhance local launcher logic with user threshold check SDKE-361

[guillermot]

Summary

Enhance local launcher logic with user threshold check. This commit implements a 50/50 traffic split mechanism for the Rokt Local Launcher feature by adding a user threshold check.

Changes Made:

Enhanced Local Launcher Logic (src/Rokt-Kit.js):

Added _isUserAboveLocalLauncherThreshold() function that implements a 50% threshold check using Math.random() > 0.5
Modified isPartnerInLocalLauncherTestGroup() to include the threshold check alongside the existing isLocalLauncherEnabled configuration
Users are now randomly assigned to either local or remote launcher based on the threshold

Comprehensive Test Coverage (test/src/tests.js):

Added test case for users below threshold (random = 0) → should create remote launcher
Added test case for users above threshold (random = 1) → should create local launcher
Added Math.random mock setup to ensure deterministic test behavior

Impact

Enables gradual rollout of the local launcher feature with 50/50 traffic split
Maintains backward compatibility with existing configuration
Provides robust test coverage for the new threshold logic

Testing Plan

{explain how this has been tested, and what additional testing should be done}