feat: Add temporary system prompt

Adds a new setting that allows users to set a temporary system prompt for the current chat.
This prompt will override the selected system prompt if it exists.
The new setting is available in the "Current Chat Model Settings" modal.
This feature provides a way to quickly experiment with different system prompts without having to change the default setting.

src/hooks/useMessageOption.tsx

@@ -68,7 +68,7 @@ export const useMessageOption = () => {
   } = useStoreMessageOption()
   const currentChatModelSettings = useStoreChatModelSettings()
   const [selectedModel, setSelectedModel] = useStorage("selectedModel")
-  const [ speechToTextLanguage, setSpeechToTextLanguage ] = useStorage(
+  const [speechToTextLanguage, setSpeechToTextLanguage] = useStorage(
     "speechToTextLanguage",
     "en-US"
   )
@@ -450,7 +450,11 @@ export const useMessageOption = () => {
         )
       }
 
-      if (selectedPrompt) {
+      const isTempSystemprompt =
+        currentChatModelSettings.systemPrompt &&
+        currentChatModelSettings.systemPrompt?.trim().length > 0
+
+      if (!isTempSystemprompt && selectedPrompt) {
         applicationChatHistory.unshift(
           new SystemMessage({
             content: [
@@ -463,6 +467,19 @@ export const useMessageOption = () => {
         )
       }
 
+      if (isTempSystemprompt) {
+        applicationChatHistory.unshift(
+          new SystemMessage({
+            content: [
+              {
+                text: currentChatModelSettings.systemPrompt,
+                type: "text"
+              }
+            ]
+          })
+        )
+      }
+
       const chunks = await ollama.stream(
         [...applicationChatHistory, humanMessage],
         {