fix(llm): add stop_sequences parity for tool completions (#1170)

* fix(llm): add stop_sequences parity for tool completions

* refactor(web-openai): dedupe request builders and satisfy no-panics gate

* test(llm): mark multiline assert with safety comment for CI gate

* test(llm): make safety-marked assert formatting-stable

src/llm/response_cache.rs

@@ -548,6 +548,7 @@ mod tests {
             model: None,
             max_tokens: None,
             temperature: None,
+            stop_sequences: None,
             tool_choice: None,
             metadata: Default::default(),
         };