[checking] elide_missing_patterns does not account for Partial via superclass entailment

Summary

In compiler-core/checking/src/core/constraint.rs, the elide_missing_patterns check (introduced in #146) uses implication_given.contains(partial) to decide whether to suppress MissingPatterns errors. This only inspects the raw/direct given set and does not account for Partial being made available through superclass entailment.

As a result, if Partial is reachable via a superclass but not listed as a direct given, MissingPatterns errors may still be emitted even though the scope should permit partiality.

Details

• File: compiler-core/checking/src/core/constraint.rs
• Relevant lines: around the elide_missing_patterns computation in collect_scoped_constraints

The fix would be to consult the elaborated/entailment-aware given set when computing elide_missing_patterns, so that Partial derived through superclass entailment also suppresses the error.

Context

Raised as a review comment on #146: https://github.com/purefunctor/purescript-alexandrite/pull/146#discussion_r3297875713

Acknowledged as a known limitation by @purefunctor — Partial is typically provided directly in practice, making this a very small class of bug unlikely to appear in real-world codebases. Tracked here for completeness.