Bug: Auto-update failed to upgrade from v1.0.58 to v1.0.59

Subject: Bug: Auto-update failed to upgrade from v1.0.58 to v1.0.59

Body:

Describe the Bug

The auto-update mechanism is failing. I am currently running v1.0.58, and the official changelog shows that a newer version, v1.0.59, is available.

Upon starting the claude CLI, it correctly detects a new version is available but then fails to perform the update, displaying the message: ✗ Auto-update failed.

The diagnostic tool (claude doctor) reports the Config install method is unknown, which strongly suggests the issue is related to the CLI being installed via bun.

To Reproduce

1. On a system with Claude CLI v1.0.58 previously installed globally using bun.
2. Launch the CLI by running claude.
3. Observe the welcome screen, which will display the auto-update failure message at the bottom.

Expected Behavior

The CLI should successfully auto-update from v1.0.58 to v1.0.59 without manual intervention, even when installed via bun.

Actual Behavior

The auto-update process fails, and the user is prompted to try claude doctor or manually reinstall with npm.

Diagnostic Information

Here is the output from my terminal:

➜  ~ claude doctor
 Claude CLI Diagnostic
 Currently running: unknown (1.0.58)
 Path: /Users/<username>/.nvm/versions/node/v22.16.0/bin/node
 Invoked: /Users/<username>/.bun/bin/claude
 Config install method: unknown
 Auto-updates enabled: true
 Press Enter to continue…

➜  ~ claude --version
1.0.58 (Claude Code)

➜  ~ claude
╭───────────────────────────────────────────────────╮
│ ✻ Welcome to Claude Code!                         │
│                                                   │
│   /help for help, /status for your current setup  │
│                                                   │
│   cwd: /Users/<username>                          │
╰───────────────────────────────────────────────────╯

╭───────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ > Try "write a test for <filepath>"                                                                           │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
  ? for shortcuts                                                                            ◯ /ide for VS Code
                                 ✗ Auto-update failed · Try claude doctor or npm i -g @anthropic-ai/claude-code

System

• OS: macOS
• Current CLI Version: 1.0.58
• Target CLI Version: 1.0.59
• Installation Method: Bun JS (bun)
• Node Version (as detected by CLI): v22.16.0