fix: sglang worker log extraction error

[KivenChen]

Overview:

Fix #361 and other potential log extraction issues for sglang workers.

Details:

The previous log extraction regex has an unreachable case (caps.len()==2, as caps always has 3 optional groups), which may misclassify or silence error logs. It might be necessary to clear the ambiguity.

Where should the reviewer start?

lib/llm/src/engines/sglang/worker.rs

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• closes GitHub issue: No error traceback for backend serving framework service start #361

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[github-actions]

👋 Hi KivenChen! Thank you for contributing to ai-dynamo/dynamo.

Just a reminder: The NVIDIA Test Github Validation CI runs an essential subset of the testing framework to quickly catch errors.Your PR reviewers may elect to test the changes comprehensively before approving your changes.

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[ryanolson]

thanks! lgtm