Library version is bumped to 1.0.0.4 with tested-with matching the new matrix

## Summary

Update the `version:` and `tested-with:` fields in `network-arbitrary.cabal` to reflect the next release and its decided GHC matrix. Regenerate `haskell-ci.yml` to match.

## Motivation

Source-of-truth bump for the next release. The epoch-scope decision (#81) found no breaking changes in the public API, so this is a patch bump — `1.0.0.4`, not `2.0.0.0`.

## Scope

- Edit `version:` to `1.0.0.4`.
- Edit `tested-with:` to the post-decision GHC matrix.
- Regenerate `.github/workflows/haskell-ci.yml`.

## Acceptance criteria

- [ ] `version: 1.0.0.4` in `network-arbitrary.cabal`.
- [ ] `tested-with:` reflects the post-decision GHC matrix.
- [ ] `haskell-ci.yml` regenerated and committed.

## Additional context

Unblocked by #81 — the epoch was retired; next release is the patch `1.0.0.4`.