[CI]: Enforce lazy export synchronization - #174

Description

Follow-up to #173.

Add a repository-specific Flake8 rule that keeps PEP 562 lazy export registries synchronized with the public module API.

• Add RMP002 to require every __lazy_imports__ key in __all__.
• Require each declaration to use one direct, statically verifiable literal assignment.
• Reject redeclarations, additional writes, and direct calls rooted at __all__ or __lazy_imports__; allow pure reads.
• Split the local plugin into independently registered AsyncSuffixChecker (RMP001) and LazyExportChecker (RMP002).
• Add focused AST tests for mixed registries, dynamic declarations, incremental construction, reads, and Flake8 wiring.
• Document the convention and register RMP002 as an external Ruff code.

Validation:

• python -m pre_commit run --all-files
• Full unit suite: 732 passed

Breaking changes

None.

Checklist

• pre-commit run --all-files passes
• Tests added or updated for changes
• Documentation updated