feat(ms-ai-architect): Sesjon 20 — B3 create_skill (dvelende, konstruktiv op) [skip-docs]

B3 + Spor B (krav 5+6) KOMPLETT. create_skill er speilbildet av de
destruktive ops: merge/saner/retire beviser "ingen kuratert verdi TAPT";
create beviser "ingen sub-bar skill FØDT" (kvalitetsgulv). Ingen ny
domene-skill shippet (svar 3) — mekanismen bevist, ikke brukt.

- planCreateSkill (ren): genererer scaffold + selv-validerer mot eval.mjs
  sine EGNE checkers (K2/K3/K5/K6/refTall + K10) — rubrikken har én kilde.
  Guardrail ok iff alle deterministiske K passerer + K10<terskel + navn ledig.
- TEST_DOMAIN_SPEC: kanonisk dvelende-scaffold (born compliant, K5 ratio 1.0).
- runCreatePlan (uren): gated dry-run, 0 skriving til skills/.
- applyApprovedAction create-gren: re-plan fersk → revalider (drift+kollisjon)
  → skriv scaffold + persister taksonomi-tillegg → flipp ledger.
- applyCategoryAdditions (taxonomy.mjs): additiv, klobrer aldri eksisterende eier.
- CLI create-verb i plan-skill-op + apply-skill-op.

TDD: ny test-skill-ops-create.test.mjs (16). kb-eval 84→100.
Suiter uendret: validate 239 · kb-update 139 · kb-integrity 192/192.
Deterministisk eval K1–K10 for de 5 ekte: 0 regresjon. 0 ekte skills/-mutasjon.

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

scripts/kb-update/lib/taxonomy.mjs

@@ -56,6 +56,26 @@ export function applyCategoryReassignments(tax, reassignments) {
   return { ...tax, category_skill: next };
 }
 
+/**
+ * Add category ownership for a NEW skill (create_skill, Sesjon 20). Pure —
+ * returns a new taxonomy, mutates nothing. For each { category, skill }, the
+ * category is assigned to `skill` ONLY when it is currently UNOWNED (absent):
+ * an existing owner is never clobbered (a create must not steal a sibling's
+ * category — that would be a merge, a different gated op). Additive counterpart
+ * to applyCategoryReassignments: reassign repoints an owned category, add claims
+ * an unowned one. The same gated apply-path is the only writer.
+ * @param {object} tax
+ * @param {Array<{category: string, skill: string}>} additions
+ * @returns {object} new taxonomy
+ */
+export function applyCategoryAdditions(tax, additions) {
+  const next = { ...tax.category_skill };
+  for (const { category, skill } of additions) {
+    if (next[category] === undefined) next[category] = skill;
+  }
+  return { ...tax, category_skill: next };
+}
+
 /**
  * Target sitemap child-name prefixes to scan/poll.
  * @param {object} tax