v0.2.3

Fixed

• The appliance workflow had never run, and died four hundredths of a second
  in. mkdir: cannot create directory '/mnt/appliance': Permission denied —
  on a GitHub runner /mnt belongs to root, and that is where the disk space
  is (~70 GB against ~14 on /). No local build could show it, since the
  directory exists and is writable on a developer's machine. A dedicated step
  now creates it with sudo and hands it to the runner.

• The image is published on every release, not only on minor ones. The old
  rule saved bandwidth and cost more than it saved: the documentation announced
  an appliance the latest release did not carry, and the reader had to work out
  which earlier release did. "The latest release carries the image" is the only
  sentence that needs no caveat, and nothing accumulates since the retention
  step keeps the last two sets. The two workflows now start from the same tag,
  so the upload waits for the Release to exist instead of assuming it — and
  says which workflow to look at if it never does.

Changed

• The documentation is a path now, not a pile of pages. Read end to end
  against the code, it had breaks that no single page could reveal:

  learner.md promised run right after cloning a catalog, while 66 of the
  Linux catalog's 86 labs are vm labs: that run exits 2, the provision
  it suggests exits 1 for want of an SSH key, and neither instructor bootstrap, nor start, nor the word Terraform appeared anywhere on the
  page. It now names what a vm lab asks of a machine, and puts start first
  — the command that plays the whole order and announces each step with the
  command that replays it alone.

  catalog-author.md listed a lab's files without saying what goes in them.
  The scale that validate-structure enforces (### … (20 pts) against a
  N tasks, M points header, and one point per test), the format of
  hints.yaml, and where conftest.py lives — pytest runs from the catalog
  root — were documented nowhere.

  The README reached neither the index nor exit-codes.md,
  machine-output.md and infra-only.md: three reference pages unreachable
  from the front door.

  The SSH key was described as something a catalog ships. It is not: published
  catalogs ignore the whole ssh/ directory, and provision refuses to start
  without the private half. It is generated per clone, by instructor bootstrap, learners included.

  contract-v1.md contradicted itself nine lines apart on whether
  repo.category is required.

• docs/appliance.md is a step-by-step, from installing VirtualBox to the
  first lab, with the digest check, the memory to give the machine depending on
  the host's, what the first boot looks like in three acts, and a
  troubleshooting table. Both READMEs open on the two ways in, each with its
  own four-step path.

Added

• Credit where it is due: the appliance is @cedric-ribier's idea, and it
  exists because he had already built one end to end and documented it in
  #91. The one shipped here
  is directly inspired by his.