Add compile-pass, compile-fail, and golden tests for solverforge-macros

[blackopsrepl]

Summary

solverforge-macros is primarily validated indirectly today.

Problem

Proc macro behavior and diagnostics are best protected by direct macro-specific regression tests.

Why This Matters

Downstream tests help, but they do not replace focused checks for expansion behavior and author-facing diagnostics.

Proposed Work

• Add compile-pass tests for key macro attribute usage.
• Add compile-fail tests for common authoring mistakes.
• Add snapshot or golden coverage for expected expansion behavior where practical.

Acceptance Criteria

• Macro-specific regression coverage exists.
• Common mistakes produce stable, intentional diagnostics.

Source

Derived from PR #3 (PRODUCTION_REVIEW_ISSUES_2026-03-20.md).

[blackopsrepl]

Resolved by #23.

We added compile-pass, compile-fail, and golden coverage for solverforge-macros, including trybuild fixtures and golden expansion assertions, and fixed the pass fixture so it does not import the same macros twice.