Add full mortgage simulation engine with distributed tranches across 5 lending tiers
(2yr/5yr/10yr/15yr/30yr), reinvestment mechanics, secondary market transfers, and
overpayment routing. Includes four visualization modes: mycelial network, Sankey flow,
lender grid, and lender return calculator comparing monthly liquidity vs reinvest-to-term
strategies. Tranches can be partially funded (open slots visible in all views).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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