Bug: Cmd+N opens duplicate conversations based on visible tab count

Description

When multiple Claude Code conversation tabs are visible in the VSCode layout and the user presses Cmd+N in a Claude Code tab, the extension opens a new conversation for each visible tab instead of just one.

Steps to Reproduce

1. Open multiple Claude Code conversation tabs (e.g., open 2-3 tabs)
2. Keep all tabs visible in the current layout
3. Focus on a Claude Code tab
4. Press Cmd+N

Expected Behavior

One new conversation tab opens

Actual Behavior

Multiple new conversation tabs open (number matches the count of visible Claude Code tabs)

Examples

• 2 visible tabs → 2 new conversations open
• 3 visible tabs → 3 new conversations open

Environment

• VSCode: Latest
• Claude Code Extension: Latest
• OS: macOS

Root Cause

Cmd+N appears to be triggered for each visible tab simultaneously rather than once globally