reimplement agent,provider and add file history

internal/llm/prompt/title.go

@@ -1,6 +1,8 @@
 package prompt
 
-func TitlePrompt() string {
+import "github.com/kujtimiihoxha/termai/internal/llm/models"
+
+func TitlePrompt(_ models.ModelProvider) string {
 	return `you will generate a short title based on the first message a user begins a conversation with
 - ensure it is not more than 50 characters long
 - the title should be a summary of the user's message