id: CORE-002C
title: Historical Workspace Collateral to GLD Share Conversion Alignment
status: backlog
priority: P1
effort: M
depends_on:
  - CORE-002A
  - CORE-001C
tags:
  - core
  - units
  - backtesting
  - event-comparison
summary: Align workspace-derived collateral defaults with explicit GLD share semantics in historical/backtest-style paths so workspace collateral is converted through named metadata rather than ad hoc share assumptions.
acceptance_criteria:
  - Backtest/event-style workspace seeding uses explicit metadata-backed collateral/share conversion rules.
  - Historical/unit materialization remains compatible while avoiding ambiguous share-vs-ounce assumptions.
  - Unsupported or missing conversion metadata fails closed.
  - Tests cover workspace-derived default seeding and changed browser-visible read paths where relevant.
technical_notes:
  - Likely file targets include `app/domain/backtesting_math.py`, `app/services/backtesting/ui_service.py`, `app/services/backtesting/comparison.py`, and `app/services/event_comparison_ui.py`.
  - Reuse the instrument metadata seam introduced in `CORE-002A`/`CORE-002B`.