Wires the existing add_random_seeds_to_gens parameter (already in
generation_orchestrator.py:824) through the full Run Settings pipeline:
1. Builder UI: state default + _addRunSetting widget (int, 0-100, default 0)
2. config_builder_node.py: emits into session_settings in configs_json
3. sampler_node.py: reads from session_settings, overrides the local variable
The generation loop already handles it — generates N extra images per config
with random seeds when > 0. Previously hardcoded to 0 with no UI path.
Based on PR #21 by external contributor, rebased onto current main with
full pipeline wiring.
Tests: 118/118 pass.