[FEATURE] file upload in Claude Code web interface

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Wish we had a means to upload a file in Claude Code web interface.
It'd be very helpful when a user is trying to explain abt an error better.

Proposed Solution

Pick the existing method that alea

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_