## Problem
An account of type `checking`/`savings` with a genuinely **negative**
balance was:
- displayed as **positive** on the dashboard account card, and
- **added** to the net worth chart instead of subtracted,
while the **accounts page** rendered the same balance correctly as
negative.
## Root cause
The dashboard used `getAccountSign(type) * Math.abs(value)`. Liabilities
(`credit_card`/`loan`) are stored as positive magnitudes, so `-abs()`
was
correct for them — but for an **asset** holding a negative balance,
`+abs()`
flipped the sign to positive and summed it into net worth. The accounts
page
was correct because it uses the raw signed balance from
`AccountMetricsService`
with no sign transform.
## Fix
- Add `netWorthContribution(type, balance)` in `chart-calculations.ts`:
liabilities subtract their magnitude, assets keep their real sign (so an
overdrawn asset correctly reduces net worth).
- Dashboard account card (`use-dashboard-data.ts`) now shows the raw
signed
balance, matching the accounts page.
- Net worth headline total, short/long trend indicators and the
stacked-asset
total (`net-worth-chart.tsx`) use the raw signed value instead of
`Math.abs`.
## Tests
- 3 new unit tests in `chart-calculations.test.ts`, including a
regression case
for a negative asset balance. Full suite: 37 passing.
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