Site 2 (BC at L224): _chunk_code had a fallback to text chunking on any
failure:
try:
parser = ASTParser('python')
tree = parser.parse(content)
...
return chunks
except Exception:
return self._chunk_text(content)
Body: broad catch + fallback to a different implementation = empty-default
fallback = SS-style violation.
New helper _chunk_code_result(content, file_path) -> Result[List[str]]:
- Returns Result(data=chunks) on AST parse success
- Returns Result(data=None, errors=[ErrorInfo]) on parse failure
Legacy _chunk_code calls helper; on Result errors, falls back to
_chunk_text (preserving original behavior). The catch logic is in the
legacy, not the helper, so the caller decides the fallback strategy.
Audit: rag_engine BC 4 -> 3.
