Refactor Sphinx setup into a shared macro

[google-labs-jules]

Here are the recommended changes in diff format:

diff --git a/gapic/ads-templates/docs/conf.py.j2 b/gapic/ads-templates/docs/conf.py.j2
index dcce591c..a2e28915 100644
--- a/gapic/ads-templates/docs/conf.py.j2
+++ b/gapic/ads-templates/docs/conf.py.j2
@@ -1,6 +1,7 @@
 {% extends '_base.py.j2' %}
 
 {% block content %}
+{% from "docs/common_setup.py.j2" import sphinx_setup %}
 
 #
 # {{ api.naming.warehouse_package_name }} documentation build configuration file
@@ -361,4 +362,6 @@ napoleon_use_admonition_for_references = False
 napoleon_use_ivar = False
 napoleon_use_param = True
 napoleon_use_rtype = True
+
+{{ sphinx_setup() }}
 {% endblock %}
diff --git a/gapic/templates/docs/common_setup.py.j2 b/gapic/templates/docs/common_setup.py.j2
new file mode 100644
index 00000000..0af8ebe7
--- /dev/null
+++ b/gapic/templates/docs/common_setup.py.j2
@@ -0,0 +1,33 @@
+{% macro sphinx_setup() -%}
+import logging
+from typing import Any
+
+class UnexpectedUnindentFilter(logging.Filter):
+    """Filter out warnings about unexpected unindentation following bullet lists."""
+
+    def filter(self, record: logging.LogRecord) -> bool:
+        """Filter the log record.
+
+        Args:
+            record (logging.LogRecord): The log record.
+
+        Returns:
+            bool: False to suppress the warning, True to allow it.
+        """
+        msg = record.getMessage()
+        if "Bullet list ends without a blank line" in msg:
+            return False
+        return True
+
+
+def setup(app: Any) -> None:
+    """Setup the Sphinx application.
+
+    Args:
+        app (Any): The Sphinx application.
+    """
+    # Sphinx's logger is hierarchical. Adding a filter to the
+    # root 'sphinx' logger will catch warnings from all sub-loggers.
+    logger = logging.getLogger('sphinx')
+    logger.addFilter(UnexpectedUnindentFilter())
+{%- endmacro %}
diff --git a/gapic/templates/docs/conf.py.j2 b/gapic/templates/docs/conf.py.j2
index b509706a..7615ca09 100644
--- a/gapic/templates/docs/conf.py.j2
+++ b/gapic/templates/docs/conf.py.j2
@@ -1,6 +1,7 @@
 {% extends '_base.py.j2' %}
 
 {% block content %}
+{% from "docs/common_setup.py.j2" import sphinx_setup %}
 
 #
 # {{ api.naming.warehouse_package_name }} documentation build configuration file
@@ -372,4 +373,6 @@ napoleon_use_admonition_for_references = False
 napoleon_use_ivar = False
 napoleon_use_param = True
 napoleon_use_rtype = True
+
+{{ sphinx_setup() }}
 {% endblock %}

Notes:

• Type hints and Google-style docstrings were added to the UnexpectedUnindentFilter class and setup function.
• The ads-templates update assumes that gapic/templates/docs/common_setup.py.j2 is accessible in the Jinja2 loader search path. If ads-templates are generated in an isolated environment where gapic/templates is not present, you may need to copy common_setup.py.j2 to gapic/ads-templates/docs/ or adjust the generator configuration to include the common templates path.

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PR created automatically by Jules for task 16614492846158068595 started by @chalmerlowe

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