Drop subplot_tracer.png fallback — quick-update writes only fit.png

The lens imaging plotter (and every other model plotter) short-circuits
with `if quick_update: return` immediately after `subplot_fit`, so the
tracer subplot is never written during a quick update. The fallback was
also stale: the `subplot_` prefix was dropped from all PNG outputs
across the codebase — the file is `tracer.png` now, not
`subplot_tracer.png`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

autofit/non_linear/quick_update.py

@@ -31,13 +31,13 @@ def _convert_jax_to_numpy(instance):
     return instance
 
 
-# Filenames the worker will look for under `paths.image_path`, in priority
-# order, when refreshing a live quick-update display. The first existing
-# file wins. PyAutoGalaxy / PyAutoLens `subplot_fit` plotters save under
-# `fit.png` (the literal "fit" basename is passed to `_save_subplot`);
-# `subplot_tracer.png` is the fallback name used by some dataset-model
-# variants that don't have a fit subplot per se.
-_DISPLAY_CANDIDATES = ("fit.png", "subplot_tracer.png")
+# Filename the worker looks for under `paths.image_path` when refreshing
+# a live quick-update display. Every dataset-type `subplot_fit` plotter
+# in PyAutoGalaxy / PyAutoLens writes this exact name — the basename
+# `"fit"` is passed to `_save_subplot` / `save_figure`, which appends
+# the `.png` extension. The `subplot_` prefix that the constant used to
+# carry no longer exists on any output anywhere in the codebase.
+_DISPLAY_CANDIDATES = ("fit.png",)
 
 
 def _is_ipython_kernel() -> bool: