feat(search-pipeline): add searchIndexerPipeline convenience

[ddeboer]

Fix #640

What

searchIndexerPipeline in @lde/search-pipeline wires the common object-grain search indexer and returns the ready-to-run Pipeline<TypedSearchDocument>:

• one stage per RootType in the schema, each selecting the type’s non-blank roots by class (selectByClass, blank-node-safe since Blank-node roots crash framing; selectByClass selects them #641 landed) and extracting with the schema-generated CONSTRUCT;
• the single searchIndexWriter terminal, one engine writer per type via writerFor;
• datasets as a plain Dataset[] (wrapped in ManualDatasetSelection) or any DatasetSelector;
• pass-through of distributionResolver (e.g. ImportResolver + @lde/sparql-qlever), provenanceStore + pipelineVersion, and reporter.

Consumers now supply only the domain (schema, datasets) and the deployment shell (engine writer, SPARQL/import adapter), instead of repeating the wiring that surfaced #633/#638 downstream. Anything beyond the object grain – bespoke selectors, per-stage tuning, non-SPARQL readers, plugins – still composes searchStages/searchIndexWriter/Pipeline directly; the convenience owns no capability of its own.

Supporting docs (the issue’s original scope)

• @lde/search-pipeline README: a Quick start for the convenience plus the role → package mapping table (selection, resolution/import via @lde/sparql-qlever, stages, engine writer via @lde/search-typesense, provenance, reporting).
• The stub READMEs of @lde/sparql-server and @lde/sparql-importer now say they are interface-only and point at @lde/sparql-qlever as the concrete adapter.

Tests

• Unit: wiring (one engine writer per root type, Dataset[] and DatasetSelector forms, pipelineVersion required with a provenance store).
• Integration (new port 3008, registered in AGENTS.md): full searchIndexerPipeline(...).run() against a local SPARQL endpoint over the Drapo fixture – both types indexed into their own committed collections, and the fixture’s blank-node CreativeWork excluded by the baked-in blank-node-safe selection.