fix(bench): validate trace spec dimensions

[blackflytech]

Describe your changes

This PR tightens miden-bench trace spec parsing so that invalid or misleading trace specifications are rejected early.

Specifically, it:

• rejects trace specs with more fields than AIR:LOG_HEIGHT[:WIDTH[:AUX_COLS]];
• rejects WIDTH / AUX_COLS for non-Miden traces, since those dimensions only apply to miden;
• keeps the existing Miden defaults for omitted dimensions;
• adds unit coverage for valid Miden specs, valid hash specs, and invalid extra dimensions.

This avoids accepting CLI input where extra fields appear meaningful but are ignored by the benchmark runner.

Checklist before requesting a review

• Repo forked and branch created from next according to naming convention.
• Commit messages and codestyle follow conventions.
• Relevant issues are linked in the PR description.
• Tests added for new functionality.
• Documentation/comments updated according to changes.

[github-actions]

Automated check (CONTRIBUTING.md)

Findings:

• Link an issue in the PR body (e.g., "Fixes feat: added enum to describe the meaning of the bit #123").
• Add a short Rationale explaining why the change is needed.

Recommendations:

• Consider adding a Test plan or clear review steps.

Next steps:

• Link a relevant issue (e.g., "Fixes feat: added enum to describe the meaning of the bit #123") and ensure it is assigned to you.
• See CONTRIBUTING.md for expectations.
• If this is a false positive, comment: /quality-review.