Agent Skills: pattern-matching

This skill should be used when the user asks about "Effect Match", "pattern matching", "Match.type", "Match.tag", "Match.when", "Schema.is()", "Schema.is with Match", "exhaustive matching", "discriminated unions", "Match.value", "converting switch to Match", "converting if/else to Match", "TaggedClass with Match", or needs to understand how Effect provides type-safe exhaustive pattern matching.