Deprecate missing-init-py in favour of ruff INP001 #25

Summary

missing-init-py is superseded by ruff's INP001 (implicit-namespace-package, from flake8-no-pep420). Users should migrate to it, and once no repo depends on this hook, this repo can be archived.

How to migrate

1. Enable the rule in your ruff config:

   [tool.ruff.lint]
   select = [..., "INP001"]
   
   # Replaces `--exclude <dir>` from this hook
   [tool.ruff.lint.per-file-ignores]
   "{doc,docker}/**" = ["INP001"]

2. Remove the hook from .pre-commit-config.yaml:

   - repo: https://github.com/hardcoretech/missing
     rev: v0.3.0
     hooks:
       - id: missing-init-py

3. Run ruff check --select INP001 . once to find the existing violations, then fix them or add them to per-file-ignores.

INP001 has been in ruff for a long time, so older pins like ruff-pre-commit v0.6.1 already include it. You don't need to upgrade ruff.

Behavior differences

The prefix-match row matters when migrating: a dir this hook never actually checked will start being checked by ruff. Run step 3 to see whether that applies to you.