Add post-processing tool: clean and plot CSV data

hioki-clean clean <file> - removes error rows and settle artifacts
after auto-range transitions. hioki-clean plot <file> - visualizes
CSV data with grouped subplots (voltage, current, power, efficiency).

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

.claude/settings.local.json

@@ -2,7 +2,8 @@
   "permissions": {
     "allow": [
       "Bash(uv:*)",
-      "Bash(rm:*)"
+      "Bash(rm:*)",
+      "Bash(python:*)"
     ]
   }
 }