Split large service test modules by responsibility

[yvette-carlisle]

Summary

• split knowledge unit tests into core, helper, memory, and search modules
• split recall debug tests into helper, layer, replay, and visibility modules
• split graph ingestion acceptance coverage into helper, note, query, and event modules while preserving the existing single-predicate submodule

Validation

• RUSTC=/run/current-system/sw/bin/rustc cargo make fmt-rust
• RUSTC=/run/current-system/sw/bin/rustc cargo make check

Batch size: 16 files changed, 2001 insertions, 1975 deletions.