perf(xsd): batch ingest inserts and preserve xml:space refs

Three independent improvements to the XSD ingest pipeline:

1. Batched multi-row INSERTs for memberships, inheritance edges, child
   edges, group edges, attr edges, enums, and the top-level symbol
   upsert pass. Compositors stay per-row since their id feeds nested
   compositor parents. Cuts ~2700 round-trips down to ~30 for the
   transitional WML closure.

2. xml:space attr refs are no longer dropped. The xml prefix is
   reserved (XML Namespaces 1.0 §3) and bound to
   http://www.w3.org/XML/1998/namespace whether the document declares
   it explicitly or not. parse-schema now binds the implicit prefix so
   resolveQNameAttr can resolve xml:space cleanly. Edges land with
   local_name='space' and attr_symbol_id=null on CT_Text and friends.

3. Optional verbose flag on ingestSchemaSet so the CLI gets one-line
   per-pass progress logs while tests and library callers stay silent.

Author: caiopizzol