Improve comments in test_figure.py for clarity

Clarified that vplanet.run() will either run the simulation or load
existing output depending on whether log files exist.

Note: Tests currently fail in CI due to "(null)" units in public vplanet
version. This is a known limitation already fixed in vplanet-private and
will be resolved when migrating to vplanet-private.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: RoryBarnes

tests/test_figure.py

@@ -12,14 +12,16 @@
 matplotlib.use("Agg")
 
 
-# Grab the output
+# Path to example directory
 path = os.path.join(
     os.path.dirname(os.path.dirname(__file__)),
     "docs",
     "notebooks",
     "examples",
     "CircumbinaryOrbit",
 )
+
+# Run vplanet (or load existing output if already run)
 output = vplanet.run(os.path.join(path, "vpl.in"))