style: fix ruff lint and formatting issues

- tts.py: rename ambiguous variable 'l' to 'line' (E741)
- tts.py, llm.py: apply ruff formatter

llm.py

@@ -168,10 +168,12 @@ async def chat_stream(
         messages.append({"role": "system", "content": system_prompt})
 
     for entry in history:
-        messages.append({
-            "role": entry["role"],
-            "content": _extract_content(entry["content"]),
-        })
+        messages.append(
+            {
+                "role": entry["role"],
+                "content": _extract_content(entry["content"]),
+            }
+        )
 
     messages.append({"role": "user", "content": message})
 
@@ -214,7 +216,9 @@ async def chat_stream(
                         continue
 
                 latency = time.time() - start_time
-                logger.info("LLM streamed response: %d chars in %.1fs", len(full_text), latency)
+                logger.info(
+                    "LLM streamed response: %d chars in %.1fs", len(full_text), latency
+                )
 
                 # Best-effort metrics from the final SSE payload
                 _log_llm_metrics(
@@ -229,9 +233,7 @@ async def chat_stream(
                 # Non-streaming fallback (endpoint doesn't support stream)
                 body = await response.aread()
                 result = json.loads(body)
-                text = _extract_content(
-                    result["choices"][0]["message"]["content"]
-                )
+                text = _extract_content(result["choices"][0]["message"]["content"])
                 latency = time.time() - start_time
                 usage = result.get("usage", {})