[codex] strengthen event ingestion validation

[stacknil]

Summary

Fixes #3.

This PR keeps scope limited to input validation and error clarity for local file ingestion. It strengthens load_events so the repository's two supported runtime formats, .jsonl and .csv, fail more predictably when input is malformed or when required event fields are missing.

Before this change, JSONL parsing already rejected invalid JSON lines, but CSV parsing mostly surfaced raw pandas exceptions, and required-field validation only checked whether a column existed anywhere in the frame. That meant a mixed JSONL or CSV file could still pass validation even if an individual record was missing a required field value, because the column existed due to other rows.

The fix does three focused things:

• wraps malformed CSV parse failures in a clear ValueError that includes the file path
• improves malformed JSONL errors so they include both the file path and line number
• strengthens required-field validation so both .jsonl and .csv inputs must provide timestamp, event_type, source, target, and status for every row/record, not just somewhere in the table

I also made a one-line README clarification so the documented required fields match the stricter runtime behavior for both supported formats.

Validation

• pytest tests/test_io.py
• pytest

Notes

I also attempted python -m pip install -e . in this environment, but it timed out locally before completion. The repository's existing editable install was already available, and the full test suite still passed against the checked-out code.

[stacknil]

@codex review
Focus on:

• whether required-field validation is now consistent across JSONL and CSV
• whether malformed-input error messages are clear but not overspecified
• whether README claims match actual loader/runtime behavior
• whether the PR stays strictly within issue v0.2: strengthen input validation for JSONL/CSV ingestion and required fields #3

[chatgpt-codex-connector]

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Reviewed commit: 9dce0d5ea2

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[stacknil]

@codex review
Please re-review the latest head commit after the CSV NA-like literal fix.
Focus on:

• whether required-field validation is now consistent across JSONL and CSV
• whether malformed-input error messages are clear but not overspecified
• whether README claims match actual loader/runtime behavior
• whether the PR stays strictly within issue v0.2: strengthen input validation for JSONL/CSV ingestion and required fields #3

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".