Add save confirmation dialog when closing app with unsaved changes

[Copilot]

App closes immediately without prompting user to save unsaved changes, risking data loss.

Changes

• TitleBar.tsx: Added save confirmation dialog using Tauri's message API with three options:
  • Save – saves file then closes (aborts close on save failure)
  • Don't Save – closes without saving
  • Cancel – returns to editor
• App.tsx: Pass handleSaveFile to TitleBar; fix missing TauriEvent import

const result = await message("Do you want to save changes before closing?", {
  title: "Unsaved Changes",
  kind: "warning",
  buttons: { yes: "Save", no: "Don't Save", cancel: "Cancel" }
});

Original prompt

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This section details on the original issue you should resolve

<issue_title>When closing asking user</issue_title>
<issue_description>So when I make some changes and close the app then the app direclty close without asking user a warning to save there work. </issue_description>

<agent_instructions>Hey there i want you to look into the code and fully understand it. when user make some change and usesr tries to close the app it should ask user to save the work and close like any normal editor app</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes When closing asking user #11

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