Move strip_toc_summary plugin to lib/ directory

The pelican-plugins/ directory is gitignored, so moved the plugin
to lib/ which is tracked. Updated PLUGIN_PATHS to include lib/.

This plugin provides the strip_anchors Jinja2 filter that removes
TOC divs and toc-backref anchor links from article summaries on
the homepage, preventing broken anchor links in excerpts.

lib/strip_toc_summary.py

@@ -0,0 +1,43 @@
+"""
+Pelican plugin to strip Table of Contents and anchor links from article summaries.
+
+This prevents TOC links and heading anchor links with invalid anchors
+from appearing on the homepage.
+"""
+from pelican import signals
+import re
+
+
+def strip_anchors(text):
+    """Jinja2 filter to strip TOC and anchor links from HTML text."""
+    if not text:
+        return text
+
+    # Remove the entire <div class="contents"> ... </div> block
+    text = re.sub(
+        r'<div\s+class="contents[^"]*"[^>]*>.*?</div>',
+        '',
+        text,
+        flags=re.DOTALL | re.IGNORECASE
+    )
+
+    # Remove anchor links from headings
+    # Converts <a class="toc-backref" href="#id1">text</a> to just text
+    text = re.sub(
+        r'<a[^>]*class="[^"]*toc-backref[^"]*"[^>]*>(.*?)</a>',
+        r'\1',
+        text,
+        flags=re.DOTALL | re.IGNORECASE
+    )
+
+    return text
+
+
+def add_filter(pelican):
+    """Add the strip_anchors filter to Jinja2."""
+    pelican.env.filters.update({'strip_anchors': strip_anchors})
+
+
+def register():
+    """Register the plugin with Pelican."""
+    signals.generator_init.connect(add_filter)

pelicanconf.py

@@ -105,7 +105,7 @@ OUTPUT_SOURCES_EXTENSION = '.rst'
 
 # Setup filters and plugins.
 
-PLUGIN_PATHS = ["pelican-plugins"]
+PLUGIN_PATHS = ["pelican-plugins", "lib"]
 PLUGINS = ["random_article", "strip_toc_summary"]
 
 # register filters.