fix: granite33 response_end span uses sentence length not full response length

_add_citation_response_spans computed response_end as index + len(response_text_without_citations),
which is the length of the entire stripped response rather than the cited sentence. This caused
every citation span to overshoot, potentially past the end of the string.

Fixes #843

Author: planetf1

mellea/formatters/granite/granite3/granite33/output.py

@@ -223,7 +223,7 @@ def _add_citation_response_spans(
 
         citation["response_text"] = response_text
         citation["response_begin"] = index
-        citation["response_end"] = index + len(response_text_without_citations)
+        citation["response_end"] = index + len(response_text)
 
     return augmented_citation_info