[ADD] personalverrechnung: General-AT plan and legal sources (M0/GP0)

Approved implementation plan for l10n_at_hr_payroll_private (M0,
decisions D1-D4) and the GP0 legal-source inventory
RECHTSQUELLEN-Privat.md, verified against primary sources (RIS,
jusline):

- FLAF-DB § 41 FLAG: 3.7% for 2026, 2.7% from 2028 (GesNr 10008220);
  KommStG 1993: 3% (GesNr 10004841)
- 13th/14th salary taxation runs via § 67 EStG (Jahressechstel fixed
  rates, control sixth § 77 Abs 4a); § 68 covers allowances/surcharges
  only - plan citation corrected, also fixes the legal basis of the
  Bgld open point P9
- Urlaubsentgelt is § 6 UrlG (§ 9 repealed since 2001) - corrected
- EOSB: no Monatsentgelt staffel; § 15 BMSVG pays out the Anwartschaft
  with § 14 Abs 2 Verfügungsausschluss matrix - GP5 design confirmed
- 2026 overtime measure: first 15 hours, max 170 €/month
  (§ 124b Z 476 lit c BGBl I 43/2026)

Plan section 8 items 3-6 and UrlG (8) marked verified; private module
skeleton README, MEMORY, CHANGELOG and payroll skill updated (§ 67
citation fix, RECHTSQUELLEN-Privat.md as required source).

.agents/skills/payroll/SKILL.md

@@ -51,6 +51,12 @@ work, combine this skill with:
    ASVG/FLAG extracts. If `.firecrawl/` is missing, re-fetch from RIS
    (ris.bka.gv.at) and sozialversicherung.at before working from
    memory.
+5. `personalverrechnung/RECHTSQUELLEN-Privat.md` — the verified legal
+   inventory for the General-AT private-economy product
+   (`l10n_at_hr_payroll_private`), GP0 2026-09. Binding for any
+   private-economy work: § 67 EStG for begünstigte Bezüge, § 6 UrlG
+   for Urlaubsentgelt, BMSVG Anwartschaft model for EOSB, § 41 FLAG
+   and KommStG for the private Dienstgeberabgaben.
 
 ## Legal model (Burgenland — verified 2026-09)
 
@@ -68,8 +74,11 @@ work, combine this skill with:
   components (§§ 61–63, 74–87).
 - **Sonderzahlung is quarterly:** 50 % of the Monatsentgelt (incl.
   Kinderzulage) per Kalendervierteljahr — not a classic 13th/14th.
-  The lohnsteuerliche mapping to begünstigte Bezüge (§ 68 Abs 5/6 EStG)
-  is a designated open point (see below).
+  The lohnsteuerliche mapping to begünstigte Bezüge runs via **§ 67
+  EStG** (GP0 2026-09 verified: § 67 = sonstige Bezüge fixed rates;
+  § 68 EStG only covers Zulagen/Zuschläge free limits); the detailed
+  LStR-2002 interpretation of the quarterly SZ remains an open point
+  (see below).
 - **€ values come from annual Bgld. Bezügeanpassungs-Sammelgesetzen**
   (tables in Anlagen/§-Ersetzungen; 2026: RV 0715/XXIII. GP / LGBl.
   50/2026) — never from a KV catalog, never hard-coded from a prior