Handle auto parsing reasoning during streaming

- Add function to handle auto parsing reasoning from the streamed message during streaming
- Only works when the reasoning prefix is EXACTLY at the beginning of the message
- Tried to keep this lightweight, no regex parsing, remembering the index, so it's simple string splicing
- Add utility function that trims a string only if `trim_spaces` is enabled

public/script.js

@@ -3223,6 +3223,7 @@ class StreamingProcessor {
 
             // Update reasoning
             await this.reasoningHandler.process(messageId, mesChanged);
+            processedText = chat[messageId]['mes'];
 
             // Token count update.
             const tokenCountText = this.reasoningHandler.reasoning + processedText;
@@ -3373,7 +3374,7 @@ class StreamingProcessor {
                     this.messageLogprobs.push(...(Array.isArray(logprobs) ? logprobs : [logprobs]));
                 }
                 // Get the updated reasoning string into the handler
-                this.reasoningHandler.updateReasoning(this.messageId, state?.reasoning ?? '');
+                this.reasoningHandler.updateReasoning(this.messageId, state?.reasoning);
                 await eventSource.emit(event_types.STREAM_TOKEN_RECEIVED, text);
                 await sw.tick(async () => await this.onProgressStreaming(this.messageId, this.continueMessage + text));
             }