fix(auth): auto-generate unique usage_id in create_llm() (#1964)

[timon0305]

Summary

When using OpenAISubscriptionAuth.create_llm() multiple times without explicit usage_id, the LLMRegistry raises ValueError because both LLMs get the default usage_id of "default".

Changes:

• create_llm() now auto-generates unique usage_id if not provided (format: chatgpt-subscription-{8_hex_chars})
• Added generate_usage_id() utility function in llm.py for consistent unique ID generation across the codebase
• Added has() and get_or_none() methods to LLMRegistry for safer registry operations
• Exported generate_usage_id from openhands.sdk.llm package

Checklist

• If the PR is changing/adding functionality, are there tests to reflect this?
• If there is an example, have you run the example to make sure that it works?
• If there are instructions on how to run the code, have you followed the instructions and made sure that it works?
• If the feature is significant enough to require documentation, is there a PR open on the OpenHands/docs repository with the same branch name?
• Is the github CI passing?

[all-hands-bot]

🟡 Acceptable - Solves a real problem pragmatically, but the implementation has "code smell" issues that violate good taste.

VERDICT: ✅ Worth merging after addressing the inconsistency

KEY INSIGHT: You built a proper utility function for ID generation but then ignored it in the actual fix—this is like bringing a hammer to a job site and using your fist instead.

[all-hands-bot]

[Automatic Post]: It has been a while since there was any activity on this PR. @timon0305, are you still working on it? If so, please go ahead, if not then please request review, close it, or request that someone else follow up.

[enyst]

Thank you for this PR, timon! I apologize for the delay, I’ve been thinking about this and I’m not sure it’s the right fix. Does it happen for subscription?

I would love to know if @VascoSch92 has thoughts, because I think maybe we will meet this problem with various profiles switches too…