feat(ms-ai-architect): Sesjon 19 — B3 merge-apply (cross-skill + taksonomi-persist) [skip-docs]

Merge-apply = den tyngste destruktive op-en: eksekver en operatør-godkjent
merge_skills-entry → faktisk cross-skill skills/-mutasjon. Tre mekanismer
som sanitize/retire ikke trengte: kuratert relokasjon (ikke arkiv),
taksonomi-persistering, retire-av-absorbert.

- taxonomy.mjs (ny persist): saveTaxonomy (atomisk .tmp+rename, speiler
  saveDecisions) + ren applyCategoryReassignments (repointer KUN der eier
  === from; absent/allerede-flyttet = no-op). Lag-0 er normalt read-only;
  ENESTE writer = gated merge-apply.
- applyApprovedAction merge-gren (skill-ops.mjs): re-plan fersk → revalidér
  (kollisjon → guardrail.ok=false → abort) → flytt absorbed-refs → absorber
  (moveFile; flyttingen ER bevaringen set-equality beviser) → persister
  taksonomi-repoint fra FERSK plan (drift-sikker) → arkivér absorbed-SKILL.md
  FØR rmdir → flipp ledger approved→applied. Description-forsoning forblir
  MANUELL (planner-kontrakt: apply rører aldri absorber-SKILL.md).
  archiveMove→moveFile (generisk: arkiv + kuratert flytt).
- CLI apply-skill-op.mjs merge <absorber> <absorbed> — lookup via actionKey
  (merge_skills:<sortert par>); default PREVIEW, --apply = dobbel-gate.

TDD, tmpdir-fixtures: 0 ekte skills/-mutasjon. Ny test-skill-ops-merge-apply
(7) + 2 taksonomi-tester; fjernet foreldet merge-throws fra S18-fila. Tester:
kb-eval 78→84, kb-update 137→139; validate 239 · kb-integrity 192/192 uendret.
eval --json deterministisk uendret (K10 eng+infra FAIL, øvrige PASS).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/kb-update/test-taxonomy.test.mjs

@@ -7,12 +7,17 @@
 
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
+import { mkdtempSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
 import {
   loadTaxonomy,
+  saveTaxonomy,
   getSitemapPrefixes,
   getCategorySkill,
   makeClassifier,
   makePriorityFn,
+  applyCategoryReassignments,
 } from '../../scripts/kb-update/lib/taxonomy.mjs';
 
 const tax = loadTaxonomy();
@@ -123,3 +128,40 @@ test('getFilePriority — order: cost (critical) outranks governance (high)', ()
   // contains both 'cost' and 'governance' — critical rule is evaluated first
   assert.equal(prio('skills/x/references/cost-governance-tradeoffs.md'), 'critical');
 });
+
+// --- (e) taxonomy persistence (Sesjon 19, B3 merge-apply) ---
+// merge-apply repoints every category owned by the absorbed skill to the
+// absorber and must PERSIST that to domain-taxonomy.json. Two new primitives:
+// a pure reassign helper + an atomic save mirroring saveDecisions.
+
+test('applyCategoryReassignments — repoints only matching from->to; pure (no mutation)', () => {
+  const before = JSON.parse(JSON.stringify(tax.category_skill));
+  const next = applyCategoryReassignments(tax, [
+    { category: 'rag-architecture', from: 'ms-ai-engineering', to: 'ms-ai-advisor' }, // matches → repointed
+    { category: 'responsible-ai', from: 'ms-ai-NONMATCH', to: 'ms-ai-advisor' },       // current != from → no-op
+    { category: 'does-not-exist', from: 'whatever', to: 'ms-ai-advisor' },             // absent category → no-op
+  ]);
+  assert.equal(next.category_skill['rag-architecture'], 'ms-ai-advisor', 'matching entry repointed');
+  assert.equal(next.category_skill['responsible-ai'], 'ms-ai-governance', 'non-matching from is a no-op');
+  assert.equal(next.category_skill['does-not-exist'], undefined, 'absent category stays absent');
+  // purity: original object + its nested map are untouched, a fresh object is returned
+  assert.deepEqual(tax.category_skill, before);
+  assert.notEqual(next, tax);
+  assert.notEqual(next.category_skill, tax.category_skill);
+});
+
+test('saveTaxonomy + loadTaxonomy — atomic round-trip preserves content', () => {
+  const dir = mkdtempSync(join(tmpdir(), 'tax-save-'));
+  try {
+    const next = applyCategoryReassignments(tax, [
+      { category: 'rag-architecture', from: 'ms-ai-engineering', to: 'ms-ai-advisor' },
+    ]);
+    saveTaxonomy(next, dir);
+    const reloaded = loadTaxonomy(dir);
+    assert.equal(getCategorySkill(reloaded, 'rag-architecture'), 'ms-ai-advisor', 'reassignment persisted');
+    assert.equal(getCategorySkill(reloaded, 'responsible-ai'), 'ms-ai-governance', 'untouched entries survive');
+    assert.equal(reloaded.version, tax.version, 'non-category_skill fields survive the round-trip');
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});