[Feature Request] Show PID of blocking process in "claude update" error message

[mithro]

Feature Description

When claude update fails because another process is updating, the error message should include the PID of the blocking process:

Current behavior:

$ claude update
Current version: 2.0.65
Checking for updates...
Another process is currently updating Claude. Please try again in a moment.

Proposed behavior:

$ claude update
Current version: 2.0.65
Checking for updates...
Another process (PID 12345) is currently updating Claude. Please try again in a moment.

Use Case

This helps users:

1. Verify if a legitimate update is in progress vs a stale lock
2. Identify and kill the blocking process if needed (kill 12345)
3. Debug issues when multiple Claude instances are running

Related Issues

• #13085 - VS Code extension causing update conflicts
• #13705 - Stale lock files blocking updates
• #6200 - Update giving "please wait" repeatedly

These are bug reports about the lock mechanism; this request is for improving the error message to aid debugging.

Environment

• Platform: Linux
• Terminal: Console (no VS Code extension)