refactor(machine): canonical sat-amount vocabulary + fix 100× fee bug

Aligns lamassu-next with the canonical sat-amount vocabulary agreed
across lnbits/bitspire/satmachineadmin (satmachineadmin@d717a6e,
coordination log 2026-05-26T17:10Z):

- `feePercent` / `cashInFeePercent` / `cashOutFeePercent`
  → `feeFraction` / `cashInFeeFraction` / `cashOutFeeFraction`
  (canonical: unit fraction in [0, 1], NEVER a percentage)
- `cashInFeeRate` / `cashOutFeeRate` (config option names)
  → `cashInFeeFraction` / `cashOutFeeFraction`
- `fee_percent` (wire field on Payment.extra + state.db column)
  → `fee_fraction`

Bug fix bundled with the rename:
`lightning.ts:780` previously stamped `Payment.extra.fee_percent =
context.feePercent * 100` (0.05 → 5.0). state.db stored the unit
fraction (0.05) but Payment.extra carried the percent (5.0) — 100×
divergence that any consumer reading Payment.extra computed fees
wrong by exactly 100×. Now stamps `fee_fraction` directly as unit
fraction. Display layers (atm-tui, view components) multiply by 100
themselves.

Defensive invariants added:
- `computeFeeSats` (atm store) throws if `feeFraction` outside [0, 1]
  or if cash-in `feeSats > principalSats` (would mean negative payout)
- `recordTransaction` (state-store) throws on the same range
- state-machine + electron + Vue views propagate the rename

state.db migration v6 → v7: `ALTER TABLE transactions RENAME COLUMN
fee_percent TO fee_fraction`. Historical migrations preserved
verbatim (they wrote `fee_percent`, future installs see the same
sequence followed by the v7 rename).

12/12 typecheck + 18/18 state-machine tests green. Coordinated with
~/dev/bitspire/atm-tui (separate commit) reading `fee_fraction`
from the new column.

refs: log:2026-05-26T17:10Z, log:2026-05-26T18:50Z,
satmachineadmin@d717a6e

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/state-machine/src/machine.ts

@@ -20,7 +20,7 @@ import {
  */
 export function createATMMachine(
   services: Partial<ATMServices> = {},
-  options?: { currency?: string; cashInFeeRate?: number; cashOutFeeRate?: number }
+  options?: { currency?: string; cashInFeeFraction?: number; cashOutFeeFraction?: number }
 ) {
   return setup({
     types: {
@@ -159,8 +159,8 @@ export function createATMMachine(
         ...initialContext,
         currency: context.currency,
         inventory: context.inventory,
-        cashInFeePercent: context.cashInFeePercent,
-        cashOutFeePercent: context.cashOutFeePercent,
+        cashInFeeFraction: context.cashInFeeFraction,
+        cashOutFeeFraction: context.cashOutFeeFraction,
         cashInSessionId: null,
         dispenseResult: null,
       })),
@@ -170,10 +170,10 @@ export function createATMMachine(
         cashInSessionId: () => generateSessionId(),
       }),
       setCashInFee: assign({
-        feePercent: ({ context }) => context.cashInFeePercent,
+        feeFraction: ({ context }) => context.cashInFeeFraction,
       }),
       setCashOutFee: assign({
-        feePercent: ({ context }) => context.cashOutFeePercent,
+        feeFraction: ({ context }) => context.cashOutFeeFraction,
       }),
       addBill: assign({
         billsInserted: ({ context, event }) => {
@@ -190,7 +190,7 @@ export function createATMMachine(
           if (context.exchangeRate === 0) return 0
           const fiatDollars = context.fiatCents / 100
           const principalSats = Math.floor(fiatDollars * context.exchangeRate)
-          const fee = Math.floor(principalSats * context.feePercent)
+          const fee = Math.floor(principalSats * context.feeFraction)
           return principalSats - fee
         },
       }),
@@ -326,7 +326,7 @@ export function createATMMachine(
           const fiatDollars = context.fiatCents / 100
           const principalSats = Math.floor(fiatDollars * context.exchangeRate)
           // For cash-out, user pays the sats, so fee is added
-          const fee = Math.floor(principalSats * context.feePercent)
+          const fee = Math.floor(principalSats * context.feeFraction)
           return principalSats + fee
         },
       }),
@@ -373,7 +373,7 @@ export function createATMMachine(
         if (context.availableBalance <= 0 || context.exchangeRate === 0) return false
         const newFiatCents = context.fiatCents + event.denomination * 100
         const principalSats = Math.floor((newFiatCents / 100) * context.exchangeRate)
-        const fee = Math.floor(principalSats * context.feePercent)
+        const fee = Math.floor(principalSats * context.feeFraction)
         return principalSats - fee <= context.availableBalance
       },
       // Cash-out guards
@@ -404,9 +404,9 @@ export function createATMMachine(
     context: {
       ...initialContext,
       ...(options?.currency ? { currency: options.currency } : {}),
-      ...(options?.cashInFeeRate !== undefined ? { cashInFeePercent: options.cashInFeeRate } : {}),
-      ...(options?.cashOutFeeRate !== undefined
-        ? { cashOutFeePercent: options.cashOutFeeRate }
+      ...(options?.cashInFeeFraction !== undefined ? { cashInFeeFraction: options.cashInFeeFraction } : {}),
+      ...(options?.cashOutFeeFraction !== undefined
+        ? { cashOutFeeFraction: options.cashOutFeeFraction }
         : {}),
     },
     states: {

packages/state-machine/src/types.ts

@@ -59,12 +59,12 @@ export interface ATMContext {
   currency: string
   /** Exchange rate (sats per fiat unit) */
   exchangeRate: number
-  /** Fee percentage (0.02 = 2%) — used at runtime for the active flow */
-  feePercent: number
-  /** Cash-in commission (0.02 = 2%) */
-  cashInFeePercent: number
-  /** Cash-out commission (0.02 = 2%) */
-  cashOutFeePercent: number
+  /** Fee as unit fraction in [0, 1] — 0.02 means 2%. Active flow's rate. */
+  feeFraction: number
+  /** Cash-in commission as unit fraction (0.02 = 2%) */
+  cashInFeeFraction: number
+  /** Cash-out commission as unit fraction (0.02 = 2%) */
+  cashOutFeeFraction: number
   /** ATM's available balance in sats (for limiting cash-in transactions) */
   availableBalance: number
 
@@ -163,9 +163,9 @@ export const initialContext: ATMContext = {
   satsAmount: 0,
   currency: 'USD',
   exchangeRate: 0,
-  feePercent: 0.0333,
-  cashInFeePercent: 0.0333,
-  cashOutFeePercent: 0.0777,
+  feeFraction: 0.0333,
+  cashInFeeFraction: 0.0333,
+  cashOutFeeFraction: 0.0777,
   availableBalance: 0,
   invoice: null,
   clinkOffer: null,