Expose reflective QBS generation

[ip332]

Expose the existing QBS v1 reflective build mode through quarry-schema-compiler.

Minimal (default):

quarry-schema-compiler \
  --emit-qbs schema.qbs \
  schema.brd

Reflective:

quarry-schema-compiler \
  --emit-qbs schema.qbs \
  --qbs-reflective \
  schema.brd

Reflective QBS includes record display names, field names, and enum type names. Symbolic enum-value names remain unsupported. Minimal QBS remains the default for compatibility and smaller embedded metadata.

For benchmarks/schemas/workload.brd, measured artifacts were:

• minimal: 881 bytes
• reflective: 1063 bytes
• increase: 182 bytes (20.66%)
• repeated reflective generation: byte-identical

The resulting workflow is .brd -> quarry-schema-compiler --emit-qbs --qbs-reflective -> reflective QBS -> quarry-brf-inspect -> human-readable field names.

This uses existing BuildMode::Reflective, QbsModelBuilder, and QBS v1 serialization. No QBS/BRF/Schema IR format changes or compatibility bumps are required.

Compatibility: C++ epoch 3, C epoch 2, Python epoch 1, BRF 2, QBS 1.

Validation: focused schema compiler tests, QBS model/serializer/parser tests, full CTest 53/53, deterministic generation, and reflective end-to-end inspection passed.