Workflow jobs have distinct names so CI checks can be required individually

## Summary

Give each CI workflow's job a distinct name so its check can be pinned as a
required status check on `main`.

## Motivation

`bats.yml`, `lychee.yml`, and `pre-commit.yml` each define their job as `run`,
so all three surface as a single check context named `run`. `astro.yml`'s job
is `build`. Classic branch protection matches required checks by context
string, so `run` can't be pinned to one workflow — only `build` is
unambiguous.

This blocks the infra side: alunduil/alunduil-infrastructure#161 (closes
alunduil/alunduil-infrastructure#27) can currently require only `build` on
`main`. Renaming these jobs unlocks requiring lint / links / bats too.
Adjacent to #216 (which adds ESLint/Prettier/workflow-lint checks).

## Scope

- Rename each workflow's job key (or set a distinct `name:`) so the check
contexts are unique, e.g. `bats`, `lychee`, `pre-commit`, `build`.
- Keep the contexts stable thereafter — required-check config references them
by string.

## Acceptance criteria

- [ ] Each CI workflow exposes a uniquely named check on a PR.
- [ ] The infra `required_status_checks` for this repo can list each check by
name without ambiguity.