VSCode extension: add native notification when Claude stops/needs input

Problem

When using Claude Code as a VSCode extension over Remote SSH, there's no way to get notified when Claude finishes and waits for input. Users often switch to other tabs/windows while Claude works, and miss when it stops.

• notify-send doesn't work on headless remote servers
• osascript can't reach the local Mac from the remote
• Hook systemMessage JSON output doesn't trigger a visible notification
• Terminal bell doesn't work because hooks run in subprocesses

Proposed Solution

Add a VSCode extension setting (e.g. claudeCode.showNotificationOnStop) that calls vscode.window.showInformationMessage() when Claude stops and waits for user input. This is similar to how GitHub Copilot shows native VSCode notification popups when tasks complete.

The extension already knows when Claude is idle (it shows a colored dot on the tab). Adding a showInformationMessage() call would be straightforward.

Environment

• Claude Code VSCode extension over Remote SSH
• macOS client → Linux server