Summary

vera/checker.py is currently 1,888 lines and growing. As C7c (visibility enforcement) and C7d (cross-module verification) land, it will approach the ~2,500 line threshold where single-file navigation becomes painful.

Suggested decomposition

Split into a vera/checker/ package:

• core.py — TypeChecker class, two-pass architecture, expression synthesis
• modules.py — cross-module registration and ModuleCall checking (C7b+)
• effects.py — effect row checking, handler validation
• __init__.py — re-export typecheck() public API

When

After C7 series completes, as a dedicated refactor phase. Splitting mid-feature would be disruptive since checker.py is modified in every C7 sub-phase.