refactor(codegen): remove pgType enrichment machinery, detect via GQL type names

Remove metaFile config, --dump-meta CLI, enrichPgTypesFromMeta/MetaFile,
buildMetaFromTables/writeMetaFile, and all associated tests.

pgvector/tsvector/PostGIS detection now relies entirely on GraphQL type
names from introspection (Vector, FullText, GeoJSON, etc.) — the codec
plugins already translate pg types to distinct GQL scalars, so no _meta
or sidecar file is needed for type detection.

M:N junction key enrichment from _meta remains (genuinely needs it).

Author: pyramation