Dependency sweep: bump litellm to 1.98.0 and refresh lockfile

[Copilot]

Description

Automated dependency sweep raising versions across the uv workspace to their latest eligible releases.

Related Issues

Automated dependency update sweep.

Proposed Changes

• packages/graphrag-llm/pyproject.toml: bumped pinned litellm==1.97.0 → 1.98.0 (the only direct dependency gated by its specifier; all other ~=X.Y specifiers already admit the latest available versions).
• uv.lock: uv lock --upgrade floated transitive deps to latest allowed (e.g. ruff 0.16.3→0.16.4, tiktoken 0.13.0→0.14.0, huggingface-hub 1.27→1.28, azure-storage-blob 12.30.0→12.30.1); litellm pulled in boto3/botocore/s3transfer.
• Held pins left untouched: graspologic-native>=1.2,<1.3 and nltk~=3.9.0 (both break golden regression data on newer majors).
• Added a patch semversioner changelog entry.

No cross-package graphrag-*== pins or version fields were modified.

Checklist

• I have tested these changes locally.
• I have reviewed the code changes.
• I have updated the documentation (if necessary).
• I have added appropriate unit tests (if applicable).

Additional Notes

All resolves used the configured Microsoft feed proxy; no version newer than the proxy's 7-day threshold was selected. poe check, test_unit (317 passed), and test_verbs (15 passed) are green.

• Fixes Update Dependencies Sweep #2529