[CHORE] Add some debug to hnsw index load

[HammadB]

Description of changes

Summarize the changes made by this PR.

• Improvements & Bug fixes
  • Add some better tracing
• New functionality
  • None

Test plan

How are these changes tested?

• Tests pass locally with pytest for python, yarn test for js, cargo test for rust

Migration plan

None

Observability plan

None

Documentation Changes

None

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[propel-code-bot]

Add structured tracing fields to HNSW S3 fetch span

Adds structured context to the existing tracing::trace_span! in HnswIndexProvider::fetch_hnsw_segment, recording the index_id and prefix_path associated with the S3 batch fetch. This enhances observability when diagnosing HNSW index loads.

Key Changes

• Extended the tracing::trace_span! call to include index_id = %source_id and prefix_path = %prefix_path

Affected Areas

• rust/index/src/hnsw_provider.rs

This summary was automatically generated by @propel-code-bot