Phase 1c: prune remaining dead functions, unused imports, quarantine Genesis

- uc480_camera: drop never-called _capture_paused/get_framerate (the
  hardware question _capture_paused encoded is now in KNOWN_ISSUES.md)
- t3r_protocol: drop read_reg/write_reg/decode_reg/Reg (commands never
  wired into the driver)
- bbd20x: drop _update0x0212 (never dispatched) and 8 of 9 unused
  trigger convenience wrappers; apt_constants: drop TriggerBitsStepper
  (servo-only rig)
- ruff --fix: 35 unused imports across all apps; drop unused T3R_BAUD
- genesis_core.py: quarantine warning header; docs/genesis_verification.md
  bench checklist for the 7 divergences vs tools/genesis_laser_gui.py

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

hardware/genesis_core.py

@@ -2,6 +2,16 @@
 Genesis SLM MX 532 Laser Core Hardware Control Module
 ======================================================
 
+.. warning::
+   QUARANTINED — do not modify semantics or dedupe against
+   ``tools/genesis_laser_gui.py`` until the bench checklist in
+   ``docs/genesis_verification.md`` has been run.  This module was
+   extracted from that GUI but diverges from it in ways only hardware can
+   adjudicate: ADS7828 command byte (0x84 vs 0x8C), LDD enable polarity
+   (inverted vs not), shutter semantics (manual vs bit-controlled),
+   dropped median-of-3 ADC filtering, dropped Amps/Watts scaling, dropped
+   temperature reads and pre-flight check.
+
 This module provides low-level hardware control for the Genesis SLM MX 532 laser
 using NXP I2C-over-serial protocol. It contains reusable classes for serial
 communication, I2C protocol handling, device control, and laser operations.
@@ -34,7 +44,6 @@ from typing import Optional, List
 from enum import IntEnum
 
 import serial
-from serial.tools import list_ports
 
 
 # ============================================================================