fix: an example in a contract shows the form of the value, and a form sent back is refused by name

[rodrigoteamx]

A contract is read by every session before it knows what it will be
asked to build. Where make and artifact:contract showed an argument
with a real name (an entity, a route, a list of fields) the contract
had chosen a domain, and whoever was later asked for that domain had
been handed part of the answer. Each example now shows the form of the
value: <Entity>, /<path>, <name>:string. So do the two refusals
that say what a page needs.

An example is copied letter for letter, so a form can come back as it
was shown. make answers that by name, before anything is scaffolded:
which argument, and what to write where the placeholder is. Two forms
used to get through: fields named <name> died later as "class not
found", and domain:verb became an operation.

The rule is tested positively and holds no list of names to avoid:
across every operation's contract, what follows an example is made of
placeholders, or is a name this package can vouch for. With the
contracts as they were, that test is red.

The second commit keeps tests/ out of the archive Composer installs.
Only tests/: the workflows and the tools stay, because the message
gate's action is fetched from this repository as an archive.