fix(cli): handle missing browser opener gracefully

[aronchick]

Problem

On headless Linux servers without xdg-open, clawhub login crashes with:

Error: spawn xdg-open ENOENT
    at ChildProcess._handle.onexit (node:internal/child_process:285:19)

This affects:

• VPS/cloud servers
• Docker containers
• CI environments
• WSL without browser integration

Solution

Catch the ENOENT error and gracefully print the URL for manual copy-paste instead of crashing.

Changes

• packages/clawdhub/src/cli/ui.ts: Add error handler to openInBrowser()

Testing

Tested on Ubuntu VPS without xdg-open installed:

Before: Crash with ENOENT
After: Prints URL with instructions to open manually

Greptile Overview

Greptile Summary

This PR updates the CLI openInBrowser() helper to handle environments where the platform opener binary (notably xdg-open on headless Linux) is missing. It adds a child.on('error', …) handler and, when the spawn fails with ENOENT, prints the URL and instructions for manual copy/paste instead of crashing.

The change is localized to packages/clawdhub/src/cli/ui.ts and affects the login flow (and any other CLI path that calls openInBrowser) by making browser-opening best-effort rather than a hard failure when the opener executable is not present.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk.
• The change is small and localized: it adds an 'error' event handler to the spawned opener process and only changes behavior in the specific failure case (missing opener binary, ENOENT) by printing a manual URL instead of crashing. No API surface changes and no control-flow changes outside the error path.
• No files require special attention

_{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!}

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