Document source UI gates, explicit native live-plot clearing, and remaining parity boundaries. Fix pause/resume transport continuity, repeated stepping, coordinate previews, and spindle override state. Optimize large program snapshots and rendering, and cover the control flows with native Tcl, WASM, and browser checks.
Validation: 22 native tests and source/browser checks pass. Worker/App regression: 113 of 123 pass; 10 pre-existing failures remain documented with no new failures.
