feat(agent): scrape linked pages to ground answers in real content

Adds `_fetch_page_content()`, which downloads a URL with a
browser-like User-Agent and uses BeautifulSoup with the lxml
parser to strip scripts, navigation, and other non-content
markup, returning up to 3000 characters of readable text.

The response validator now also compares generated replies
against this scraped text, flagging named entities and claims
that do not appear in the retrieved page content.

Dependencies: adds beautifulsoup4==4.12.3 and pins lxml==5.3.0
for parser compatibility.

venv/lib/python3.11/site-packages/lxml/includes/libxml/xpointer.h

@@ -28,10 +28,88 @@
 extern "C" {
 #endif
 
+#if defined(LIBXML_XPTR_LOCS_ENABLED)
+/*
+ * A Location Set
+ */
+typedef struct _xmlLocationSet xmlLocationSet;
+typedef xmlLocationSet *xmlLocationSetPtr;
+struct _xmlLocationSet {
+    int locNr;		      /* number of locations in the set */
+    int locMax;		      /* size of the array as allocated */
+    xmlXPathObjectPtr *locTab;/* array of locations */
+};
+
+/*
+ * Handling of location sets.
+ */
+
+XML_DEPRECATED
+XMLPUBFUN xmlLocationSetPtr
+		    xmlXPtrLocationSetCreate	(xmlXPathObjectPtr val);
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrFreeLocationSet	(xmlLocationSetPtr obj);
+XML_DEPRECATED
+XMLPUBFUN xmlLocationSetPtr
+		    xmlXPtrLocationSetMerge	(xmlLocationSetPtr val1,
+						 xmlLocationSetPtr val2);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRange		(xmlNodePtr start,
+						 int startindex,
+						 xmlNodePtr end,
+						 int endindex);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRangePoints	(xmlXPathObjectPtr start,
+						 xmlXPathObjectPtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRangeNodePoint	(xmlNodePtr start,
+						 xmlXPathObjectPtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRangePointNode	(xmlXPathObjectPtr start,
+						 xmlNodePtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRangeNodes	(xmlNodePtr start,
+						 xmlNodePtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewLocationSetNodes	(xmlNodePtr start,
+						 xmlNodePtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewLocationSetNodeSet(xmlNodeSetPtr set);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewRangeNodeObject	(xmlNodePtr start,
+						 xmlXPathObjectPtr end);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrNewCollapsedRange	(xmlNodePtr start);
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrLocationSetAdd	(xmlLocationSetPtr cur,
+						 xmlXPathObjectPtr val);
+XML_DEPRECATED
+XMLPUBFUN xmlXPathObjectPtr
+		    xmlXPtrWrapLocationSet	(xmlLocationSetPtr val);
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrLocationSetDel	(xmlLocationSetPtr cur,
+						 xmlXPathObjectPtr val);
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrLocationSetRemove	(xmlLocationSetPtr cur,
+						 int val);
+#endif /* defined(LIBXML_XPTR_LOCS_ENABLED) */
+
 /*
  * Functions.
  */
-XML_DEPRECATED
 XMLPUBFUN xmlXPathContextPtr
 		    xmlXPtrNewContext		(xmlDocPtr doc,
 						 xmlNodePtr here,
@@ -40,6 +118,18 @@ XMLPUBFUN xmlXPathObjectPtr
 		    xmlXPtrEval			(const xmlChar *str,
 						 xmlXPathContextPtr ctx);
 
+#if defined(LIBXML_XPTR_LOCS_ENABLED)
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrRangeToFunction	(xmlXPathParserContextPtr ctxt,
+						 int nargs);
+XML_DEPRECATED
+XMLPUBFUN xmlNodePtr
+		    xmlXPtrBuildNodeList	(xmlXPathObjectPtr obj);
+XML_DEPRECATED
+XMLPUBFUN void
+		    xmlXPtrEvalRangePredicate	(xmlXPathParserContextPtr ctxt);
+#endif /* defined(LIBXML_XPTR_LOCS_ENABLED) */
 #ifdef __cplusplus
 }
 #endif