fix: Handle FileData structure from backend in UI components

[sureshattaluri]

Problem

When clicking on files in the UI, a runtime error occurs: codeTree.value[0].value.split is not a function.

The root cause is a type mismatch between the backend and frontend:

• Backend: Sends files as FileData objects with structure {content: string[], created_at: string, modified_at: string}
• Frontend: Expected files as plain strings in Record<string, string>

Solution

This PR fixes the type mismatch by:

1. Added FileData type (src/app/types/types.ts)

   • Defined FileData interface matching backend structure
   • Kept FileItem for UI layer with plain string content

2. Updated useChat hook (src/app/hooks/useChat.ts)

   • Changed StateType.files to Record<string, FileData>
   • Added helper functions to convert FileData to plain strings
   • Updated event handler to convert FileData before passing to parent

3. Updated page component (src/app/page.tsx)

   • Updated thread state fetching to expect Record<string, FileData>
   • Converted FileData objects to strings when setting local state
   • Added same helper functions for consistency

Changes

• src/app/types/types.ts: Added FileData interface
• src/app/hooks/useChat.ts: Type updates and conversion logic
• src/app/page.tsx: Thread state handling updates

Testing

The fix maintains clean separation:

• API layer works with structured FileData objects
• UI layer works with plain strings
• Conversion happens at the boundary

This ensures files can now be clicked and viewed without errors while preserving all file metadata from the backend.

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