Plan mode: cannot return to plan tab after switching sessions in VS Code

Problem

When working with multiple Claude Code sessions in VS Code, the plan document tab gets lost when switching between sessions. There is no way to reopen the plan for inline commenting after the tab is closed or lost.

Steps to reproduce

1. Open multiple Claude Code sessions in VS Code
2. Enter plan mode in one session — plan opens as a separate editor tab
3. Switch to another session (or accidentally close the plan tab)
4. Try to return to the plan for inline commenting — not possible

Current behavior

• Plan opens as a temporary editor tab that can be lost
• No command or UI to reopen the plan document for the active session
• Plan files exist in ~/.claude/plans/ but reopening them manually doesn't restore inline commenting functionality

Expected behavior

Either:

• A command/button to reopen the current session's plan document at any time
• Plan displayed inline within the session panel (not as a separate tab)
• Plan tab pinned/preserved when switching between sessions

Additional context

• Token waste: The plan is sent as context regardless of whether the user can see/interact with it, increasing token consumption unnecessarily
• Multi-session workflow is a common pattern (e.g., different tasks in different sessions) — plan mode should support this gracefully
• This makes plan mode practically unusable for users who regularly work with 2+ sessions

Environment

• VS Code (Windows 11)
• Claude Code extension (latest)