Add support for Foundation.Predicate

[colemancda]

Resolves #15

Converts predicates built with the #Predicate macro into FetchRequest.Predicate by walking the PredicateExpressions tree, cross-platform via swift-foundation's FoundationEssentials — and extends the CoreModel predicate model and in-memory evaluator so everything CoreData can represent converts and evaluates consistently.

Foundation.Predicate conversion

• New throwing initializer FetchRequest.Predicate.init(_: Foundation.Predicate<T>) (macOS 14 / iOS 17 / tvOS 17 / watchOS 10, matching Foundation.Predicate availability).
• Comparisons (==, !=, <, <=, >, >=), compounds (&& / || flattened into single compounds, !), contains, starts(with:), localizedStandardContains (Darwin, mapped to CONTAINS[cd]), boolean properties used directly as predicates, constants, and nil comparisons.
• Arithmetic: +, -, *, /, %, and unary minus convert to the new ArithmeticExpression.
• Collection closures: allSatisfy { ... } and contains(where:) { ... } convert to ALL/ANY modifier comparisons via variable-binding contexts (single-comparison tests; compound tests throw).
• Aggregates: min() / max() convert to @min / @max key path operators.
• Ranges: 18...30 lowers to >= lower && <= upper, half-open 18..<30 to >= lower && < upper (BETWEEN isn't evaluatable).
• Key paths resolve to property names via Key-Value Coding on Darwin, falling back to parsing the key path's reflection-based debugDescription, so plain Swift structs work on all platforms.
• Regex: contains(regex) converts to a MATCHES comparison. The macro wraps regexes in PredicateExpressions.PredicateRegex, which retains the source pattern, so literals, Regex(String), and RegexBuilder regexes all convert; the pattern is padded with .* because MATCHES matches the whole value (requires macOS 15 / iOS 18, where those types are available).
• Unsupported expressions (subscripts, type casts, ??, nested closures) throw a descriptive ConversionError instead of silently misconverting.

CoreModel predicate model

• New FetchRequest.Predicate.ArithmeticExpression (add/subtract/multiply/divide/modulus) as a new Expression case, with Codable support and in-memory evaluation: integer operands stay integral, division is always floating-point (matching NSExpression's divide:by:), division by zero and floating-point remainder resolve to no match.
• Relationship key path traversal in the in-memory evaluator: events.name now resolves through to-one and to-many relationships against an object index, so ALL/ANY predicates produce the same results in memory as they do in CoreData. Previously these silently matched nothing. FetchRequest.evaluate(_:) builds the index from the objects it is given, and InMemoryStorage now supplies every entity's objects so relationships resolve.

CoreDataModel

• Arithmetic expressions bridge to NSExpression(forFunction:) — the Function raw values are the NSExpression function names.
• Function detection for the in-memory fallback path recurses into arithmetic operands.

Tests

• ArithmeticExpressionTests: CoreModel API construction, description, Codable round-trip, evaluation semantics (promotion, division by zero, non-numeric operands), fetch request evaluation.
• FoundationPredicateTests: every supported #Predicate expression shape, converted-tree assertions, in-memory filtering, and error paths.
• KeyPathTraversalTests: to-one and to-many traversal, ALL/ANY, unresolved relationships, InMemoryStorage fetches, and the same traversals built with #Predicate.
• CoreDataModelTests: end-to-end fetches against a CoreData store using arithmetic and ALL/ANY predicates built both from #Predicate and the CoreModel API, including a check that empty to-many ALL is vacuously true in CoreData and that the in-memory evaluator agrees on the same objects.

[github-code-quality]

Code Coverage Overview

Languages: Swift

Swift / code-coverage/llvm-cov

The overall coverage in commit 818c137 in the feature/predicate branch remains at 95%, unchanged from commit fff8b7b in the master branch.

Show a code coverage summary of the most impacted files.

File	master fff8b7b	feature/predicate 818c137	+/-
Sources/CoreMod...Predicate.swift	0%	85%	+85%