feat(ms-ai-architect): Sesjon 3 - decision-ledger (lag 2) + discovery-dedup

Lukker discovery-løkken gjennom operatør-gaten. data/decisions.json er eneste
skrive-autoriserte bro mellom deteksjon og KB/registry; discovery LESER den og
utelater alt operatøren har tatt stilling til.

Dedup-policy = A (operatør-valg): isDecided = enhver ledger-entry (approved/
rejected/pending). Kun helt fraværende URLer re-foreslås.

- lib/decisions-io.mjs: createLedger/load/save(atomisk)/isDecided/recordDecision
  (ren)/filterUndecided. TDD: 10 tester før kode.
- discover-new-urls.mjs leser ledger, filtrerer, rapporterer deduped_by_ledger.
  Importerer ALDRI write-utils (invariant verifisert, 6 guard-tester).
- Gate dokumentert i kb-update.md §3b (eneste skrivevei).
- decisions.json tracket via gitignore-negasjon (som domain-taxonomy.json).

Kriterium møtt: dedup-diff (rejected re-foreslås ikke runde 2).
Tester: validate 239 · kb-update 82 (+16) · kb-eval 13 · kb-integrity 115/115.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01REiKFhP4w6xGXXqWKpPCJJ

tests/kb-update/test-discover-invariant.test.mjs

@@ -0,0 +1,44 @@
+// tests/kb-update/test-discover-invariant.test.mjs
+// Architecture-invariant guard (STATE.md §83 / roadmap §159): the detection
+// script discover-new-urls.mjs must NEVER import write-utils. It only READS the
+// decision ledger to filter; all writes go through the operator gate. saveReport
+// (its own discovery-report.json) is allowed — that is detection's own output,
+// not a KB/registry mutation.
+
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const DISCOVER = join(__dirname, '..', '..', 'scripts', 'kb-update', 'discover-new-urls.mjs');
+const src = readFileSync(DISCOVER, 'utf8');
+
+// Sjekkene er IMPORT-spesifikke med vilje: en invariant-guard som brytes av en
+// kommentar som *beskriver* invarianten er verdiløs. Vi gransker import-linjer.
+const importLines = src.split('\n').filter((l) => /^\s*import\b/.test(l)).join('\n');
+
+test('discover does NOT import the ledger write path (saveDecisions)', () => {
+  assert.doesNotMatch(importLines, /\bsaveDecisions\b/);
+});
+
+test('discover does NOT import the registry write path (saveRegistry)', () => {
+  assert.doesNotMatch(importLines, /\bsaveRegistry\b/);
+});
+
+test('discover does NOT import atomic-write', () => {
+  assert.doesNotMatch(importLines, /from\s+'[^']*atomic-write[^']*'/);
+});
+
+test('discover does NOT import backup', () => {
+  assert.doesNotMatch(importLines, /from\s+'[^']*\/backup\.mjs'/);
+});
+
+test('discover DOES read the ledger (loadDecisions from decisions-io)', () => {
+  assert.match(src, /import \{[^}]*\bloadDecisions\b[^}]*\} from '\.\/lib\/decisions-io\.mjs'/);
+});
+
+test('discover actually applies the dedup filter (isDecided)', () => {
+  assert.match(src, /isDecided\(/);
+});