feat(mcp): onboarding flow v2: migration-first SIE import in chat, one-confirm momentum, extended first-year heuristic (#1949)

Three changes from the first real E2E run (Arcim, 2026-08-26):

1. gnubok_sie_preflight: read-only scan of a SIE file shared in chat
   BEFORE anything is staged: parse, validate (per-verifikat balance, IB,
   closed-year P&L residual), CP1252-mojibake tripwire, duplicate
   file/period check, org-number match against the company (the
   wrong-company import is the worst silent failure this flow can have),
   and suggested account mappings shaped for direct passthrough to
   gnubok_import_sie. Both tools now also accept file_content_base64,
   decoded with the same encoding detection as the HTTP upload route so
   CP437 exports keep their åäö.

2. Onboarding skill v2: opens with TWO questions (orgnr + 'vilket system
   hade du innan?'), imports history before the bank (PSD2 rarely reaches
   far enough back), and a momentum rule: the create preview is the ONLY
   stop; connect tools are called without asking, and categorization
   starts as soon as the bank is active. connect_bank instructions now
   describe the account-selection dialog that actually gates the first
   sync, and the bank history cap.

3. deriveFirstYearDefaults: no closed fiscal period in the registry now
   extends the first-year window from 12 to 18 months (BFL 3 kap 3 §):
   a 13-month-old company with no annual report is still in its first,
   extended räkenskapsår (the Arcim case the 12-month rule missed).
   Applied in the web journey and the lookup tool.

tools/list ceiling 61.5K to 62K, documented in the bench.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/company/__tests__/first-year-defaults.test.ts

@@ -46,6 +46,18 @@ describe('deriveFirstYearDefaults', () => {
     expect(deriveFirstYearDefaults(registered, NOW).isFirstFiscalYear).toBe(false)
   })
 
+  it('extends the window to 18 months when the registry shows no closed period', () => {
+    // Extended first räkenskapsår (BFL 3 kap 3 §): registered 13 months ago
+    // with no annual report filed is still the first year.
+    const registered = NOW - 13 * MONTH_MS
+    expect(
+      deriveFirstYearDefaults(registered, NOW, { noClosedPeriod: true }).isFirstFiscalYear
+    ).toBe(true)
+    expect(
+      deriveFirstYearDefaults(NOW - 19 * MONTH_MS, NOW, { noClosedPeriod: true }).isFirstFiscalYear
+    ).toBe(false)
+  })
+
   it('seeds first_year_start as the 1st of the UTC registration month', () => {
     const registered = new Date('2026-03-14T10:00:00Z').getTime()
     const result = deriveFirstYearDefaults(registered, NOW)

lib/company/first-year-defaults.ts

@@ -22,16 +22,21 @@ export function parseStartMonthDay(value: string | null | undefined): number | n
 /**
  * Derive the first-year defaults from TIC's `registrationDate`.
  * A company is treated as "first year" when registered less than 12 months
- * ago: comfortably inside BFL's 18-month cap on a first räkenskapsår, which
- * has no minimum length. Returns both the toggle state and a seeded
- * `first_year_start` (always the 1st of the registration month, the format
- * the date inputs expect).
+ * ago, or less than 18 months ago when the registry shows NO closed fiscal
+ * period (`noClosedPeriod`): a company that has never filed an annual
+ * report is still in its first räkenskapsår, and BFL 3 kap 3 § allows that
+ * first year to run up to 18 months (no minimum). The 12-month floor alone
+ * missed exactly the extended-first-year companies the signal exists for
+ * (Arcim, registered 13 months before onboarding, first year to 31 Dec).
+ * Returns both the toggle state and a seeded `first_year_start` (always the
+ * 1st of the registration month, the format the date inputs expect).
  *
  * `now` exists for tests; production callers omit it.
  */
 export function deriveFirstYearDefaults(
   registrationDate: number | null | undefined,
   now: number = Date.now(),
+  opts?: { noClosedPeriod?: boolean },
 ): {
   isFirstFiscalYear: boolean
   firstYearStart: string | undefined
@@ -43,8 +48,9 @@ export function deriveFirstYearDefaults(
   if (Number.isNaN(regDate.getTime())) {
     return { isFirstFiscalYear: false, firstYearStart: undefined }
   }
+  const windowMonths = opts?.noClosedPeriod ? 18 : 12
   const monthsAgo = (now - regDate.getTime()) / (1000 * 60 * 60 * 24 * 30.44)
-  if (monthsAgo >= 12) return { isFirstFiscalYear: false, firstYearStart: undefined }
+  if (monthsAgo >= windowMonths) return { isFirstFiscalYear: false, firstYearStart: undefined }
   const year = regDate.getUTCFullYear()
   const month = String(regDate.getUTCMonth() + 1).padStart(2, '0')
   return { isFirstFiscalYear: true, firstYearStart: `${year}-${month}-01` }