engine: db/tests.rs is 79 lines from the 6000-line per-file lint cap #645

Problem

src/simlin-engine/src/db/tests.rs is at ~5921 / 6000 lines. The repo-wide lint (scripts/lint-project.sh, MAX_LINES=6000, enforced in pre-commit and CI) will trip on the next non-trivial test addition, blocking an unrelated commit until someone does a tangential split.

This is the same class of problem as #518 (db.rs), #588 (vm.rs), and #471 (vdf.rs), but for a distinct file: the salsa-incremental test module.

Why it matters

db/tests.rs is a high-traffic test file for the salsa incremental pipeline -- new incremental-compilation and analysis tests land here regularly. The next addition over ~79 lines will fail pnpm lint on an unrelated diff. Splitting it now (with headroom) is lower-risk than under duress.

What's in db/tests.rs

The file already has clean // -- section headers that map to natural sibling test files:

• Accumulator parity
• Incremental sync
• Incremental compilation
• AC acceptance
• PREVIOUS / INIT

Possible approach

Split db/tests.rs into 2-3 sibling test files along the existing section headers, following the #[path = "..."] mod ...; submodule precedent already used in the db/ module.

Component

• src/simlin-engine/src/db/tests.rs
• Lint rule in scripts/lint-project.sh

Severity

low / maintenance.

Context

Identified during the salsa-pipeline-cleanup refactor.