Add more vectors coverage

[siv2r]

Address bitcoin/bips#2070 (comment), except different $(t, n)$ suggestion

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: d8c2b64702

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".

[claude]

Architectural Review - Summary

This PR significantly expands test vector coverage for FROST signing, adding approximately 500 lines with new error cases and improved documentation.

Strengths:

1. Expanded Error Coverage: Adds important edge cases for out-of-range identifiers, zero-valued secret shares, secnonce validation, and point-at-infinity tweaking
2. Improved Error Messages: More descriptive messages aid debugging
3. Better Documentation: Test vectors summary is valuable

Concerns:

1. Removed Test Cases: Several validation tests were removed including checks for mismatched counts and pubshare validation. Question: Are these now redundant or moved elsewhere?
2. Test Maintenance Complexity: Vector generation has grown more complex with conditional overrides and computed tweaks. Consider adding more inline documentation.
3. Vector File Format: JSON formatting changes may affect machine parsing - ensure tools are tested.

Recommendations:

• Verify test coverage to ensure removed cases don't leave gaps
• Document test categories and their BIP specification references
• Consider organizing vectors into subcategories for scalability

Verdict: Valuable improvements pending fixes to inline issues (particularly reconstruct_thresh_sk validation) and clarification on removed test cases.

[mllwchrry]

I reviewed the test vectors, and everything looks good. Do you plan to add coverage for different threshold settings in another PR?

[siv2r]

Thanks for the review. Yes, I'm currently looking into it.