Replace all cross-thread root.after() calls with a queue.Queue drained by
the main thread's _schedule_update() timer. _TextHandler no longer holds a
widget reference; log append runs on the main thread via _drain_ui_queue().
Also adds adi_agc_analysis.py — one-off bit-accurate RTL AGC simulation
for ADI CN0566 raw IQ captures (throwaway diagnostic script).
Jason