feat(search-api-graphql): write the GraphQL contract of a schema module to a file - #722

A deployment that mounts a schema-declaration module usually wants its GraphQL
contract as a published file – schema.graphql, the thing consumers read
and pull requests diff. Today each such repository writes that generator
itself; Linked Open Limburg has one, and it is generic apart from its paths.
This moves it here.

search-print-sdl

search-print-sdl --module ./dist/module.js --out ./schema.graphql

Loads the module through loadSchemaModule from @lde/search/module – the
same loader, the same validation and the same schemaOptions forwarding the
indexer and the served API use – so the printed file cannot describe a
different API from the one served. Without --out the SDL goes to standard
output.

printSchemaModuleSdl is the same thing from code, on a
@lde/search-api-graphql/print-sdl entry point rather than the barrel: it
reads the filesystem, and the main entry point stays runtime-agnostic for
consumers bundling the fetch handler for workers or the edge (mirroring how
@lde/search keeps loadSchemaModule on /module).

Formatting

The output is formatted with the Prettier configuration that applies to the
output path, .editorconfig included – the Prettier CLI reads it by default
and the Node API does not, so leaving it off would have a repository’s
prettier --write pre-commit hook reformat what was just written, the two
overwriting each other in turn and producing a permanent spurious diff in the
regenerate-and-commit workflow. The graphql parser is named outright, so an
output path Prettier cannot map to a parser (.sdl) formats instead of failing.

Prettier is an optional peer dependency: the consumer’s own version formats
the file, which is the point – a bundled copy at another version could reopen
the same ping-pong – and it stays out of the @lde/search-api-server image.
--no-format never loads it.

Also here

@lde/search-api-server validated its optional module exports with its own
copy of a check this writer needed too. That check now lives once, as
optionalObjectExport in @lde/search/module, next to the loader that hands
back the raw exports for consumers to validate.

Two coverage baselines move down: both packages are at 100% for every file
this touches, and the aggregate branch percentage drops only because the
deleted duplicate’s covered branches left the denominator.

Note on the lockfile

package-lock.json carries ~60 lines beyond the dependencies added here:
version drift nx release left behind by bumping package manifests without
syncing the lock. Any npm install reproduces it; hand-editing it back out is
riskier than the noise.