Task: Implement Hotfix: xsdcpp domain drift on compositeTradeComponents SubTrade

Regenerate domain.hpp/domain.cpp from the current external/ore/xsd/instruments.xsd so the compositeTradeComponents type matches the upstream subTradeGroup/SubTrade schema, and fix any downstream code that referenced the old Trade element.

• domain.hpp/domain.cpp regenerated and reflect subTradeGroup/SubTrade.
• Project builds cleanly.
• Composite-trade XML with SubTrade round-trips.

Root cause (from investigation on 2026-07-31): instruments.xsd's compositeTradeComponents type was updated upstream to use subTradeGroup/SubTrade (the old Trade element is now commented out in the XSD), but domain.hpp/domain.cpp were never regenerated to match. Plan:

1. Re-run xsdcpp codegen against the current instruments.xsd.
2. Diff generated domain.hpp/domain.cpp against the checked-in versions to isolate the SubTrade-related changes.
3. Fix any call sites depending on the old Trade element/API.
4. Build and verify round-trip of a composite trade sample using SubTrade elements.

Two independent bugs were involved, not just the schema drift:

1. xsdcpp bug (fixed upstream in ~/Development/xsdcpp, fix-abstract-element-refs branch, uncommitted local fix): pass 1 of Reader::process() interleaved group-definition collection with eager resolution of substitutionGroup elements, file by file. When a substitutionGroup element (e.g. input.xsd's top-level Trade) referenced a group defined in a file scanned later in the same pass (e.g. oreTradeData in instruments.xsd), the lookup failed because that file's groups hadn't been collected yet — group lookup returned "not found" even though the group existed. Fixed by splitting pass 1 into two full sub-passes: 1a collects group definitions across every file, 1b then resolves substitutionGroup elements once all groups are known.
2. xsdcpp_generate_ore.sh pointed at a stale path: it targeted projects/ores.ore/include|src, left over from before ores.ore was split into core/api/service. Domain.hpp/domain.cpp actually live under projects/ores.ore/core/{include,src}. Fixed the wrapper script to point at the real location (and generalised xsdcpp_generate.sh with --header-output=/--cpp-output= overrides so per-component paths don't have to fit the flat projects/PROJECT/{include,src} template).

Once regeneration actually landed in the right place, two further gaps surfaced:

1. xsdcpp has no notion of this project's hidden-by-default symbol visibility convention (doc/knowledge/external/shared_library_symbol_visibility.org), so every ORES_ORE_CORE_EXPORT annotation on domain.hpp (a hand-patch) was silently dropped by regeneration, along with the #include "ores.ore.core/export.hpp" line — this broke linking for every consumer of load_data/save_data/to_string. Wrote scripts/reapply_export_macros.py to diff the pre-regen file against the freshly generated one and reapply the macro to matching declarations by (whitespace-normalised) signature; wired it into xsdcpp_generate_ore.sh so future regenerations preserve it automatically.
2. compositeTradeComponents/trsUnderlyingData's Trade vector became a subTradeGroup vector of subTradeGroup_group_t (Trade/SubTrade substitution-group members); cdsConventionsType's Calendar, Frequency, PaymentConvention, Rule and DayCounter became optional. Updated composite_instrument_mapper.cpp and conventions_mapper.cpp accordingly.

Separately, upstream ORE removed the MultiLegOption trade type entirely (not renamed) in commit 1f9361860 ("QPR-13903 support xccy swaptions", merged 2026-04-30): Swaption gained native cross-currency-leg support, so the MultiLegOption workaround for cross-currency legs became redundant. Removed the corresponding forward/reverse mapper functions, dispatch cases, and doc-comment mentions from ORE Studio to match.

Regenerated the 10 stale Hybrid_* golden fixtures (assets/test_data/golden_dataset/Products/Example_Trades/) that encoded the old Trade-element serialisation shape.

Full repo build (compass build, no target) is green, and ores.ore.core.tests passes all 478 test cases / 428669 assertions.

Manual QA scenarios (scaffolded via compass add test_scenario, run through the QA Validation Runner panel) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

Regenerated domain.hpp/domain.cpp against the current instruments.xsd (subTradeGroup/SubTrade). Fixed two xsdcpp bugs blocking regeneration (premature group-reference resolution in Reader::process() pass 1; stale output paths in xsdcpp_generate_ore.sh from before the core/api/service split), and two hand-patch gaps regeneration exposed (missing ORES_ORE_CORE_EXPORT annotations/export.hpp include, now reapplied automatically via scripts/reapply_export_macros.py). Updated composite_instrument_mapper.cpp and conventions_mapper.cpp for the new schema shapes, and removed the MultiLegOption trade type (deleted upstream, not renamed). Regenerated the 10 stale Hybrid_* golden fixtures. Full repo build green; ores.ore.core.tests 478/478 passed (428669 assertions).