Installation fails with 'another process is currently installing' even when no other process exists

Bug Description

The installation script intermittently fails with the error:

"Could not install - another process is currently installing Claude. Please try again in a moment."

This happens even when no other installation process is running.

Steps to Reproduce

1. Run curl -fsSL https://claude.ai/install.sh | bash -s 2.0.76 - fails
2. Run the same command again - same failure
3. Run curl -fsSL https://claude.ai/install.sh | bash -s 2.0.74 - fails
4. Run with stable tag - succeeds (installs 2.0.67)
5. Run with latest tag - succeeds (installs 2.0.76)
6. Run with specific version 2.0.76 again - fails again

The behavior is inconsistent: specific version numbers fail, but stable/latest tags work.

Environment

• OS: macOS (Darwin 25.2.0)
• Architecture: Apple Silicon (darwin)
• Shell: zsh
• Current installed version: 2.0.76

Terminal Logs

$ curl -fsSL https://claude.ai/install.sh | bash -s 2.0.76
Setting up Claude Code...

✘ Installation failed

Could not install - another process is currently installing Claude. Please try again in a moment.

Try running with --force to override checks

$ curl -fsSL https://claude.ai/install.sh | bash -s stable
Setting up Claude Code...

✔ Claude Code successfully installed!
  Version: 2.0.67

$ curl -fsSL https://claude.ai/install.sh | bash -s latest
Setting up Claude Code...

✔ Claude Code successfully installed!
  Version: 2.0.76

$ curl -fsSL https://claude.ai/install.sh | bash -s 2.0.76
Setting up Claude Code...

✘ Installation failed

Could not install - another process is currently installing Claude. Please try again in a moment.

Expected Behavior

1. Installation with specific version numbers should work consistently
2. If a stale lock exists, provide a way to clear it automatically or show the lock file location

Possible Cause

The lock mechanism may be creating a stale lock file when installing specific versions, but not when using stable/latest tags. The lock file might not be properly cleaned up.