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>

pyproject.toml

@@ -0,0 +1,26 @@
+[project]
+name = "mppt-testbench"
+version = "0.1.0"
+description = "MPPT tracker testbench: IT6500D (solar sim) + Prodigit 3366G (load) + HIOKI 3193-10 (power analyzer)"
+requires-python = ">=3.12"
+dependencies = [
+    "matplotlib>=3.10.8",
+    "pyvisa>=1.16.2",
+    "pyvisa-py>=0.8.1",
+    "pyserial>=3.5",
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["testbench"]
+
+[tool.hatch.build.targets.wheel.force-include]
+"IT6500D/it6500" = "it6500"
+"PRODIGIT-3366G/prodigit3366g" = "prodigit3366g"
+"HIOKI-3193-10/hioki3193" = "hioki3193"
+
+[project.scripts]
+mppt = "testbench.cli:main"