fix(articles): article ROT/RUT prefill was dead for every dashboard-created article (#1651)

* fix(articles): article ROT/RUT prefill was dead for every dashboard-created article

Follow-up to #1634. The user re-tested and picking a RUT article still left
the line on "Ingen": the article form has always stored the bare kind
('ROT'/'RUT'), while the prefill only recognised Skatteverket work-type codes
(BYGG, STAD, ...). On prod every dashboard-created ROT/RUT article holds the
bare kind, so the fix in #1634 never fired for a real user, and worse, since
the helper returned null for those values, picking such an article CLEARED a
deduction the user had set manually on the row.

- rot-rut-rules: parseArticleHouseworkType() understands both vocabularies
  (code -> kind + arbetstyp; bare ROT/RUT -> kind only), plus
  normalizeHouseworkType()/HOUSEWORK_TYPE_VALUES/workTypeLabel().
- InvoiceEditor.applyArticle: kind-only articles pre-fill the deduction and
  keep a same-kind arbetstyp already chosen on the row; "Spara som artikel"
  round-trips the code or, lacking one, the kind.
- ArticleForm: the ROT/RUT select now offers the real Skatteverket arbetstyper
  in ROT/RUT groups (its own hint always promised "förifyller arbetstyp");
  legacy kind-only values stay selectable as "RUT (arbetstyp ej vald)" so an
  edit never silently drops the flag. Article detail renders "RUT · Städning"
  instead of the raw code.
- API + MCP commit schemas normalize housework_type (case-insensitive code or
  ROT/RUT, '' clears) and reject anything else; the CSV article import
  normalizes the column the same way. Prod holds 178 articles with '0'/'1'
  from a boolean "Rot" column that the keyword detector mapped straight
  through; those now read as no flag everywhere and can no longer be created.

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

* fix(articles): review follow-ups on #1651

- InvoiceEditor: switching a row's skattereduktion ROT<->RUT clears an
  arbetstyp from the other list, and Spara som artikel only round-trips a
  work type that belongs to the row's kind (CodeRabbit).
- MCP update_article: null / '' / whitespace now clear housework_type
  (commit drops only undefined keys, so the old undefined mapping made the
  flag un-clearable); create keeps treating them as unset. Tests.
- Article CSV import warns when a non-empty ROT/RUT value is dropped as
  not-an-arbetstyp instead of dropping it silently. Test.
- Hint wording: arbetstyp is pre-filled only when the article carries one.

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

---------

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

lib/api/__tests__/schemas.test.ts

@@ -1,4 +1,5 @@
 import { describe, it, expect } from 'vitest'
+import { HouseworkTypeSchema } from '../schemas'
 import {
   // Enums
   EntityTypeSchema,
@@ -2871,3 +2872,28 @@ describe('CreateSalaryLineItemSchema: derived-only item types', () => {
     expect(UpdateSalaryLineItemSchema.safeParse({ item_type: 'bonus' }).success).toBe(true)
   })
 })
+
+describe('HouseworkTypeSchema (articles.housework_type)', () => {
+  it('stores a Skatteverket work-type code upper-cased', () => {
+    expect(HouseworkTypeSchema.parse('stad')).toBe('STAD')
+    expect(HouseworkTypeSchema.parse('BYGG')).toBe('BYGG')
+  })
+
+  it('accepts the bare kind ROT / RUT (deduction only, no arbetstyp pre-fill)', () => {
+    expect(HouseworkTypeSchema.parse('rut')).toBe('RUT')
+    expect(HouseworkTypeSchema.parse('ROT')).toBe('ROT')
+  })
+
+  it('treats empty string as clear and passes null/undefined through', () => {
+    expect(HouseworkTypeSchema.parse('')).toBeNull()
+    expect(HouseworkTypeSchema.parse('   ')).toBeNull()
+    expect(HouseworkTypeSchema.parse(null)).toBeNull()
+    expect(HouseworkTypeSchema.parse(undefined)).toBeUndefined()
+  })
+
+  it('rejects values the invoice editor could never interpret', () => {
+    for (const bad of ['1', '0', 'Ja', 'SNICKERI', 'RUT-städning']) {
+      expect(HouseworkTypeSchema.safeParse(bad).success).toBe(false)
+    }
+  })
+})