docs: shared PyAuto brand layer for the Furo docs

Phase B of the docs middle path (pyautolabs.github.io#1; census
PyAutoLabs/PyAutoFit#1341): adds the stack-wide docs/_static/pyauto.css
(identical file in PyAutoFit/PyAutoGalaxy/PyAutoLens — the PyAuto family
gradient strip and sidebar wordmark styling) and this project's Furo accent
via light_css_variables/dark_css_variables: #0f766e / #2dd4bf (teal).

Sphinx warning count unchanged vs baseline; docs CI (phase A) guards it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GziFkivBHz1d11eFYUszmy

Author: 2 people

docs/_static/pyauto.css

@@ -0,0 +1,32 @@
+/* PyAuto shared docs brand layer — identical file in PyAutoFit, PyAutoGalaxy,
+   PyAutoLens (docs/_static/pyauto.css). The per-project accent is set via
+   Furo's color-brand-* variables in each repo's conf.py; this file carries
+   the elements common to the whole stack. */
+
+/* The PyAuto family signature: a thin gradient strip across the top of every
+   docs page, running through the three stack accents (Fit / Galaxy / Lens). */
+body::before {
+  content: "";
+  position: fixed;
+  top: 0;
+  left: 0;
+  right: 0;
+  height: 3px;
+  background: linear-gradient(90deg, #c2410c 0%, #0f766e 50%, #7c4dff 100%);
+  z-index: 1000;
+  pointer-events: none;
+}
+@media (prefers-color-scheme: dark) {
+  body:not([data-theme="light"])::before {
+    background: linear-gradient(90deg, #f28c38 0%, #2dd4bf 50%, #9d7aff 100%);
+  }
+}
+body[data-theme="dark"]::before {
+  background: linear-gradient(90deg, #f28c38 0%, #2dd4bf 50%, #9d7aff 100%);
+}
+
+/* Project wordmark in the sidebar. */
+.sidebar-brand-text {
+  font-weight: 700;
+  letter-spacing: -0.01em;
+}

docs/conf.py

@@ -124,6 +124,20 @@
 
 language = "en"
 
+html_static_path = ["_static"]
+html_css_files = ["pyauto.css"]
+
+html_theme_options = {
+    "light_css_variables": {
+        "color-brand-primary": "#0f766e",
+        "color-brand-content": "#0f766e",
+    },
+    "dark_css_variables": {
+        "color-brand-primary": "#2dd4bf",
+        "color-brand-content": "#2dd4bf",
+    },
+}
+
 from sphinx.builders.html import StandaloneHTMLBuilder
 
 StandaloneHTMLBuilder.supported_image_types = ["image/gif", "image/png", "image/jpeg"]