fix(salary): book lonevaxling pension provision from frozen run snapshot (#1382)

The book flow never populated pension_contribution/pension_slp, so a
gross_deduction_pension line item reduced the salary entry but the
7410/2740 pension provision and 7533/2514 SLP lines were never posted.
Derive both at the createSalaryRunEntries boundary from the run's frozen
calculation_params.slpRate snapshot so the dashboard, MCP and v1 booking
paths all emit the pension verifikat, and reuse the exact 1.058 factor
via calculateLoneVaxlingPensionProvision shared with the planning
calculator.

Fixes #317

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/salary/__tests__/book-run.test.ts

@@ -41,6 +41,7 @@ const makeRun = (overrides: Record<string, unknown> = {}) => ({
   total_net: 23000,
   total_avgifter: 9426,
   total_vacation_accrual: 0,
+  calculation_params: { slpRate: 0.2426 },
   ...overrides,
 })
 
@@ -194,5 +195,11 @@ describe('bookPaidSalaryRun', () => {
     expect(result.ok).toBe(true)
     if (result.ok) expect(result.data.entryIds).toEqual(['je-1', 'je-2'])
     expect(createSalaryRunEntries).toHaveBeenCalledTimes(1)
+    expect(createSalaryRunEntries).toHaveBeenCalledWith(
+      expect.anything(),
+      'company-1',
+      'user-1',
+      expect.objectContaining({ calculation_params: { slpRate: 0.2426 } }),
+    )
   })
 })

lib/salary/__tests__/salary-entries.test.ts

@@ -83,6 +83,7 @@ function makeRun(employees: ReturnType<typeof makeEmployee>[]) {
     total_net: employees.reduce((s, e) => s + e.net_salary, 0),
     total_avgifter: employees.reduce((s, e) => s + e.avgifter_amount, 0),
     total_vacation_accrual: employees.reduce((s, e) => s + e.vacation_accrual, 0),
+    calculation_params: { slpRate: 0.2426 },
     employees,
   }
 }
@@ -276,6 +277,36 @@ describe('salary entries: dimensions propagation (PR8)', () => {
     assertBalanced(pension)
   })
 
+  it('derives pension + SLP from gross_deduction_pension line items', async () => {
+    const run = makeRun([
+      makeEmployee({
+        employee_id: 'a',
+        default_dimensions: { '1': 'KS01' },
+        line_items: [
+          {
+            item_type: 'gross_deduction_pension',
+            amount: -2000,
+            account_number: '7218',
+            is_net_deduction: false,
+            is_gross_deduction: true,
+          },
+        ],
+      }),
+    ])
+
+    const result = await createSalaryRunEntries(makeSupabase(), 'company-1', 'user-1', run)
+    const pension = entryByDescription('Pensionsavsättning')
+
+    expect(result.pensionEntry).not.toBeNull()
+    expect(linesOn(pension, '7410')).toEqual([
+      expect.objectContaining({ debit_amount: 2116, dimensions: { '1': 'KS01' } }),
+    ])
+    expect(linesOn(pension, '2740')[0].credit_amount).toBe(2116)
+    expect(linesOn(pension, '7533')[0].debit_amount).toBe(513.34)
+    expect(linesOn(pension, '2514')[0].credit_amount).toBe(513.34)
+    assertBalanced(pension)
+  })
+
   it('rejects an invalid bag (coerce gate) rather than booking junk keys', async () => {
     const run = makeRun([
       makeEmployee({ employee_id: 'a', default_dimensions: { '0': 'BAD' } as Record<string, string> }),