/clear resets working directory when inside a worktree

Bug Description

Running /clear while inside a git worktree (created via EnterWorktree) resets the working directory back to the project root instead of preserving the current worktree path.

Expected Behavior

/clear should reset conversation context (message history, tasks, plans) but preserve the current working directory.

Actual Behavior

/clear resets both conversation context AND the working directory — moving from the worktree back to the main project root.

Steps to Reproduce

1. Enter a worktree (e.g., via EnterWorktree or navigating to an existing one at .claude/worktrees/<id>)
2. Confirm you're in the worktree directory on the feature branch
3. Run /clear
4. Observe the status line now shows the main project root and main branch instead of the worktree path and feature branch

Screenshots

Before /clear:

• Working directory: ~/dev/atelier/.claude/worktrees/agent-<hash>
• Branch: some-branch

After /clear:

• Working directory: ~/dev/<repo>
• Branch: main

Environment

• macOS (Darwin 25.3.0)
• Claude Code CLI