VSCode: Add setting to disable default file attachment

Feature Request

When using the Claude Code VSCode extension, the currently opened file is automatically attached to each message by default. This requires manually toggling it off (via the file tag button or Cmd+D) every time you don't want to include the file.

Proposed Solution

Add a claudeCode.autoAttachFile setting (default: true) that allows users to disable automatic file attachment. When set to false, the file attachment toggle would start in the off state.

Use Case

• Users who frequently switch between file-related and general questions
• Reduces noise when the opened file is irrelevant to the question
• Avoids accidentally sending file contents unnecessarily

Alternatives Considered

Currently the only way to control this is via the UI toggle (Cmd+D) or clicking the file tag before each message, which is tedious for users who rarely need file context attached.