Teach accounts, sizing, and constraints across asset settings #113

Affected library: backtest
Current version: 0.1.8
Location: accounts and constraints tutorial

Problem

The account and configuration pages list settings but do not show how cash, margin, shorting, quantity type, and risk limits change a common portfolio scenario.

Required outcome

Provide a controlled tutorial comparing cash and margin policies, long and short exposure, integer and fractional quantities, and position and portfolio constraints. Show rejected orders and constrained sizing in result records. State the asset conventions for each variant and link to book portfolio-construction examples.

Acceptance criteria

• Every setting produces the displayed cash, position, and rejection outcome from the documented input.
• Comparisons change only the stated setting and make the resulting difference inspectable.
• Installed-wheel checks and the strict MkDocs build pass.

Depends on the shared tutorial inputs.