test(search): add end-to-end snippet assertions for #860

Adds full-path tests that drive DocumentSearch.search() over a real
Document and assert SearchResult.snippet highlights the correct
characters (text and regex modes), complementing the existing
helper-level tests. Ported from the equivalent PR #860.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dgunning

tests/issues/regression/test_issue_860_search_snippet_offsets.py

@@ -6,7 +6,39 @@
 wrong characters.
 """
 
-from edgar.documents.search import DocumentSearch
+from edgar.documents.document import Document
+from edgar.documents.nodes import DocumentNode, ParagraphNode, TextNode
+from edgar.documents.search import DocumentSearch, SearchMode
+
+
+def _document_with_text(text: str) -> Document:
+    """Build a minimal one-paragraph document for end-to-end search tests."""
+    root = DocumentNode()
+    paragraph = ParagraphNode()
+    paragraph.add_child(TextNode(content=text))
+    root.add_child(paragraph)
+    return Document(root=root)
+
+
+def test_text_search_snippet_highlights_match_after_truncated_prefix():
+    """End-to-end: text search highlights the right characters in .snippet."""
+    text = f"{'a' * 60} target {'b' * 60}"
+    result = DocumentSearch(_document_with_text(text)).search("target")[0]
+
+    assert result.context[result.start_offset:result.end_offset] == "target"
+    assert "**target**" in result.snippet
+
+
+def test_regex_search_snippet_highlights_match_after_truncated_prefix():
+    """End-to-end: regex search highlights the right characters in .snippet."""
+    text = f"{'a' * 60} target phrase {'b' * 60}"
+    result = DocumentSearch(_document_with_text(text)).search(
+        r"target\s+phrase",
+        mode=SearchMode.REGEX,
+    )[0]
+
+    assert result.context[result.start_offset:result.end_offset] == "target phrase"
+    assert "**target phrase**" in result.snippet
 
 
 def test_get_context_with_offsets_adjusts_for_truncation():