Add setting to disable auto-attaching IDE selection/active file by default (VS Code extension)

What

The VS Code extension automatically attaches the current editor selection and active file path to every prompt (the "eye" icon in the input box, shown as ⧉ Selected N lines from <file>). The eye can be toggled off, but the state is per-session only — it resets every session.

Request

Add a persistent setting (e.g. an extension setting like attachSelectionByDefault / shareIdeSelection, or a ~/.claude/settings.json key) to make the eye off by default, so the auto-attach doesn't have to be disabled manually each session.

Why

Some workflows don't want the active file silently included on every prompt — for context hygiene and to avoid unintentionally pulling unrelated open files into the conversation. A Read deny rule only covers specific known paths and doesn't change the default toggle behavior.

Environment

• Claude Code VS Code extension
• Platform: Linux (WSL2)