fix(skattekonto): route AGI draw back to 2731 to match salary module (#1905)

* fix(skattekonto): route AGI draw back to 2731 to match salary module (#1870)

Migration 20260519160000 moved the skattekonto AGI seed to 2730 while the
salary module kept crediting 2731, splitting the employer-contribution
liability across two accounts that never net at account level (both carry
SRU 7231, so only huvudbok reconciliation exposes the drift). Revert the
system seed to 2731: BAS 2026 defines 2731 as the reported-but-unpaid
arbetsgivaravgift liability (the accrual account is 2940), and the salary
ore-residual logic is built around 2731.

Historical 2730 debits since 2026-05-19 are left for per-company reclass
verifikat; the migration touches the system seed only.

Fixes #1870

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(skattekonto): bump migration version to avoid collision with 20260825120000_create_company_for_user

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(payroll): align remaining 2730 guidance surfaces on 2731 (#1870)

Skeptic regression finding: companies booking salary manually were taught
7510/2730 by in-product guidance, so the seed revert alone would re-create
the #1870 split mirrored for them. Align every guidance surface on 2731:

- packs/loneutbetalning.yaml legal_note
- MCP payroll-monthly skill (booking recipe and rate notes)
- swedish-payroll SKILL.md + references/bas-7xxx.md (2731 convention, 2730
  group-account alternative, never mixed; accrual is 2940) + regenerated
  agent atom seed (skills:generate -> 20260825180001)
- public/docs/systemdokumentation-mall.md

Also addresses the compliance review finding that the swedish-payroll skill
contradicted the migration.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

scripts/.skill-body-manifest.json

@@ -100,16 +100,16 @@
     "version": 2
   },
   "horizontal/swedish-payroll": {
-    "hash": "8cbedb0245ae1f3a042bc2310d9563424ed58ef9fc6f3e853693844323653faa",
-    "version": 4
+    "hash": "b9d3a10d1c949b01185df001b08f150ebbaeca88bb837913bd9edab6f90e3859",
+    "version": 5
   },
   "horizontal/swedish-payroll/agi-filing": {
     "hash": "91aa490472fafff434088301dd193ed474589b36ae22bdaab640b42bc3b3c255",
     "version": 1
   },
   "horizontal/swedish-payroll/bas-7xxx": {
-    "hash": "6e7167788b3d2f9442163e29b77e79703bfc3394ff90223d2d9d096554638437",
-    "version": 1
+    "hash": "61464f317f81e9bb55d6d65a747a457b85440b076145ed44cd4055b2f0d3c324",
+    "version": 2
   },
   "horizontal/swedish-payroll/benefits": {
     "hash": "bb4ead2f45691bc84c09b7433e3b2c719c93b54f702978cfd362b125ae9c8ca2",