60aa9f5f

A rule that sees a whole package

Stacked on #6. Review that first; this diff is against it.

Adds `HsGenValidInGenPackage` from `haskell-style.md`, the first rule that
cannot answer from one module, and with it the fact store that lets a rule see
further.

39 files, 1,182 lines. 255 tests.

## Why a database

What a rule above the module level does with facts is join them. One table per
fact, owned by the rule that writes it, so a rule brings its own schema the way
it brings its own check. The envelope never learns what is in that table, which
is why adding a rule adds no case to it: a package rule is a migration, what it
writes out of one module, and the query it answers with.

A fact is a row rather than a keyed entry. Two instances in one module are two
facts, and there is nothing to key them on that is not invented.

## The level

A rule's constructor is also its level, so nothing can disagree with it. Each
level judges exactly the suppressions naming its own rules, which is what keeps
unused-suppression detection sound without a global pass over the repository.

## Still not here

One process, so the store has nowhere to go and nothing crosses a process
boundary. Nothing reads what the compiler wrote down: the package check's
signature does not take the compiler's answers, because this rule has no use
for them.

weeder removed seven store queries on the way in that only a project rule would
want.

## Review loop

```
nix flake check
nix develop --command cabal test hopinion-test --test-options="--ai-executor"
```
hlint-checkpre-commitreleaseshellweeder-checkconfiguredevShelldefaultx86_64-linux