perf: skip savefig rendering in PYAUTO_FAST_PLOTS mode

When PYAUTO_FAST_PLOTS=1, skip fig.savefig() in save_figure() and
subplot_save(). The figure is still created, data computed, and all
matplotlib drawing calls (imshow, plot, etc.) still execute — only
the final rendering to file is bypassed. This avoids expensive font
discovery and text metrics computation during smoke tests.

Also cache the env var lookup at module import time for efficiency.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

autoarray/plot/utils.py

@@ -12,14 +12,17 @@
 logger = logging.getLogger(__name__)
 
 
+_FAST_PLOTS = os.environ.get("PYAUTO_FAST_PLOTS") == "1"
+
+
 def tight_layout():
     """Call ``plt.tight_layout()`` unless fast-plot mode is active.
 
     When ``PYAUTO_FAST_PLOTS=1`` the expensive layout-optimisation pass
     is skipped.  All figure creation, data computation, and rendering
     still execute — only the final spacing adjustment is bypassed.
     """
-    if os.environ.get("PYAUTO_FAST_PLOTS") == "1":
+    if _FAST_PLOTS:
         return
     plt.tight_layout()
 
@@ -338,6 +341,10 @@ def subplot_save(fig, output_path, output_filename, output_format=None):
     if _output_mode_save(fig, output_filename):
         return
 
+    if _FAST_PLOTS:
+        plt.close(fig)
+        return
+
     if output_format == "show" or not output_path:
         plt.show()
     else:
@@ -508,6 +515,10 @@ def save_figure(
     if _output_mode_save(fig, filename):
         return
 
+    if _FAST_PLOTS:
+        plt.close(fig)
+        return
+
     formats = format if isinstance(format, (list, tuple)) else [format]
 
     if all(f == "show" for f in formats) or not path: