fix: skip tool_use blocks lacking an id

[HeaTTap]

What & why

A transcript with a tool_use block lacking an id crashed parse_session with KeyError instead of skipping the block. This PR ensures tool_use blocks without an id are safely skipped, matching the sibling tool_result handling.

Closes #19

Changes

• In agentrace/parse.py, safely retrieve the id from tool_use blocks and only store when present.
• In tests/test_agentrace.py, add test_tool_use_without_id_is_skipped asserting transcripts with id-less tool_use blocks parse without error.

Checklist

• Focused change with a clear description
• Ran format / lint / tests (see README)
• Updated docs or CHANGELOG if relevant
• Linked any related issue (e.g. Closes #123)

[github-actions]

Welcome, @HeaTTap, and thanks for your first pull request to Agentrace.

A quick look at CONTRIBUTING.md covers how things are set up and run here.

I'll review this shortly. Ask anything in the thread if something is unclear.

[github-actions]

And it's in. Thanks @HeaTTap.

Contributions like this are what keep Agentrace moving.

A star on the repo would mean a lot if this project is useful to you.

Happy to see more from you whenever you have the time.