Worktree flag hangs silently with branch names containing slashes

Description

Using the -w / --worktree flag with a branch name containing / causes Claude Code to hang silently — no output, no error. The process must be killed with Ctrl+C.

Replacing / with - in the same branch name works fine.

This was working correctly until recently (as of ~2026-03-23).

Steps to reproduce

# Hangs silently — no output, no error
claude -w "rodz/open-9825-prevent-inconsistencies-when-changing-themes-at-preferences"

# Works fine
claude -w "open-9825"

# Also works (slash replaced with dash)
claude -w "rodz-open-9825-prevent-inconsistencies-when-changing-themes-at-preferences"

Expected behavior

Claude Code should either:

1. Create/enter the worktree normally (as it did before), or
2. Show a clear error message if the branch name is invalid

Additional context

• Other worktrees with / in the name already exist in the .worktrees directory and were created successfully in prior sessions
• OS: macOS (Darwin 24.1.0)
• This is a regression — / in worktree names worked until recently