Vitest API Phase 1: Add matchers (toContainEqual, toStrictEqual, toMatchObject, toMatch)

[frostney]

Parent: #114

Summary

Add self-contained matchers to TGocciaExpectationValue in Goccia.Builtins.TestAssertions.pas that require no new infrastructure.

Matchers

• toMatch(string) — string-only initially (regex variant deferred to Add regular expression support (RegExp constructor and /pattern/flags literals) #115)
• toContainEqual(value) — deep equality check within arrays (uses existing DeepEqual logic)
• toStrictEqual(value) — strict deep equality with class instance awareness
• toMatchObject(obj) — partial/subset object matching

Implementation notes

• All matchers follow the existing pattern: method on TGocciaExpectationValue, respects FIsNegated, calls AssertionFailed() on mismatch
• toStrictEqual differs from toEqual by checking constructor identity and not allowing type coercion
• toMatchObject recursively checks that every key in the expected object exists in the actual with matching values (subset check)
• Tests should run in both TestRunner and Vitest