# Domain layer

`message.h` defines immutable Message and metadata concepts, role/tier enums,
input limits, deep-copy ownership, and UTF-8 validation. This layer has no mcpc
or Win32 dependency.

`search.h` owns the ASCII-case-folded Unicode codepoint 2/3-gram inverted index,
collision verification, candidate selection, and deterministic relevance score.

`memory_tier` is descriptive in v1. Retention, summarization, and automatic tier
transitions are intentionally not domain behaviors yet.