Initial MPPT testbench: unified CLI for IT6500D + Prodigit 3366G + HIOKI 3193-10

Combines three instrument drivers (as git submodules) into a single
testbench for MPPT tracker efficiency testing. Features:
- Voltage sweep and load current sweep with CSV export
- Auto-range aware meter polling (waits for HIOKI to settle)
- Supply keepalive during long meter waits to prevent USB-TMC timeouts
- Live monitoring with real-time 4-panel matplotlib graphs
- Safe shutdown (load first, then supply)
- Post-sweep returns to 75V idle with supply ON

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

testbench/__init__.py

@@ -0,0 +1,11 @@
+"""MPPT Tracker Testbench.
+
+Combines three instruments for solar MPPT converter testing:
+  - IT6500D:       DC power supply (solar panel simulator)
+  - Prodigit 3366G: DC electronic load
+  - HIOKI 3193-10:  Power analyzer (efficiency measurement)
+"""
+
+from testbench.bench import MPPTTestbench
+
+__all__ = ["MPPTTestbench"]