test: add compare_analyzer tools for G-code slice comparison

Add two standalone Python tools for deep comparison and analysis of .3mf
slicing project files:

- compare_slices.py: comprehensive slice comparison with filament usage,
  nozzle mapping, tool change sequences, prime tower analysis, temperature
  timeline, and automatic critical discrepancy detection
- show_temp_plot.py: interactive HTML temperature timeline plotter for
  visualizing heater profiles during multi-nozzle prints

Both tools use only Python stdlib (no external dependencies).
Primary use case: regression testing H2C carousel purge volumes and
BBS compatibility verification.

tests/compare_analyzer/README.md

@@ -0,0 +1,88 @@
+# Compare Analyzer — G-code Slicing Comparison Tools
+
+Tools for deep comparison and analysis of `.3mf` slicing project files, designed for
+verifying multi-nozzle (H2C carousel) and multi-extruder slicing correctness.
+
+## Tools
+
+### `compare_slices.py` — Slice Comparison Analyzer
+
+Deep comparison of two `.3mf` files (OrcaSlicer, BambuStudio, or any compatible slicer).
+Generates a comprehensive Markdown report covering:
+
+- **Filament usage** — per-filament weight/length with color mapping
+- **Nozzle/extruder mapping** — Vortek carousel slot assignments
+- **Tool change sequences** — T-code ordering and count
+- **Prime tower analysis** — tower entries, G-code line count
+- **Temperature timeline** — pre-heat lead times, target temperatures per tool change
+- **Retract parameters** — M620.11 analysis during nozzle switches
+- **Filament change G-code blocks** — line-by-line diff of change_filament_gcode
+- **Control command diff** — timeline of M/G-code differences
+- **Critical discrepancy detection** — automatic flagging of weight/time anomalies
+
+#### Usage
+
+```bash
+# Compare two slice files
+python3 compare_slices.py file1.3mf file2.3mf
+
+# With custom labels
+python3 compare_slices.py file1.3mf file2.3mf --labels "Upstream" "Fixed"
+```
+
+#### Output
+Markdown report saved to `mp_reports/compare_report_YYYYMMDD_HHMMSS.md`
+
+#### Example: Detecting H2C purge regression
+```
+⚠️ CRITICAL DISCREPANCY: Huge difference in part weight:
+  OrcaSlicer 60.90 g vs BambuStudio 17.47 g (difference 43.43 g or 71.3%).
+  The reason is incorrect nozzle mapping, causing huge AMS flushing.
+```
+
+---
+
+### `show_temp_plot.py` — Temperature Timeline Plotter
+
+Generates interactive HTML temperature plots for analyzing thermal profiles during
+multi-nozzle prints. Visualizes heater temperature commands (M104/M109) per tool change,
+showing pre-heat timing and temperature convergence.
+
+#### Architecture
+- H2C dual-extruder layout with Vortek carousel nozzles
+- Physical heaters mapped dynamically:
+  - Heater 0: Extruder 2 (right nozzle slot, T0/T2/T3/T4)
+  - Heater 1: Extruder 1 (left nozzle slot, T1)
+- Active heater mapping derived from G-code temperature signals
+
+#### Usage
+
+```bash
+# Single file analysis
+python3 show_temp_plot.py file.3mf
+
+# Side-by-side comparison of two files
+python3 show_temp_plot.py file1.3mf file2.3mf
+```
+
+#### Output
+Interactive HTML report saved to Desktop as `temp_plot_v3.html`
+
+---
+
+## Requirements
+
+- **Python 3.8+**
+- **No external dependencies** — uses only Python standard library
+  (`json`, `zipfile`, `xml.etree.ElementTree`, `difflib`, `webbrowser`)
+
+## Use Cases
+
+1. **Regression testing** — compare slices before/after code changes to verify
+   no unintended differences in purge volumes, tool ordering, or temperature timing
+2. **BBS compatibility verification** — compare OrcaSlicer output against BambuStudio
+   reference slices to ensure behavioral parity
+3. **H2C carousel validation** — verify per-slot nozzle tracking produces correct
+   purge volumes (not collapsed per-extruder)
+4. **Temperature protocol analysis** — verify pre-heat lead times and cooling
+   temperatures during nozzle changes match expected profiles