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

scripts/kb-update/discover-new-urls.mjs

@@ -9,6 +9,9 @@ import { normalizeUrl } from './lib/url-normalize.mjs';
 import { loadRegistry, saveReport } from './lib/registry-io.mjs';
 import { streamSitemap, fetchSitemapIndex } from './lib/sitemap-stream.mjs';
 import { loadTaxonomy, getSitemapPrefixes, makeClassifier } from './lib/taxonomy.mjs';
+// Read-only: detection filters against the ledger but NEVER writes it (arkitektur-
+// invariant — no saveDecisions / registry / atomic-write / backup imports here).
+import { loadDecisions, isDecided } from './lib/decisions-io.mjs';
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const DATA_DIR = join(__dirname, 'data');
@@ -33,6 +36,13 @@ async function main() {
   const knownUrls = new Set(Object.keys(registry.urls));
   console.log(`Registry: ${knownUrls.size} known URLs`);
 
+  // Decision ledger (lag 2): skip anything the operator already decided on
+  // (policy A — approved | rejected | pending all dedup). Read-only here.
+  const decisions = loadDecisions(DATA_DIR);
+  const decidedCount = Object.keys(decisions.decisions || {}).length;
+  console.log(`Decision ledger: ${decidedCount} decided URLs (excluded from re-proposal)`);
+  let dedupedByLedger = 0;
+
   console.log('Fetching sitemap index...');
   const indexEntries = await fetchSitemapIndex();
 
@@ -55,6 +65,7 @@ async function main() {
       for await (const entry of streamSitemap(child.loc)) {
         const normalized = normalizeUrl(entry.loc);
         if (!normalized || knownUrls.has(normalized)) continue;
+        if (isDecided(decisions, normalized)) { dedupedByLedger++; continue; }
 
         const classification = classifyUrl(normalized);
         if (!classification) continue;
@@ -89,6 +100,7 @@ async function main() {
   const report = {
     generated_at: new Date().toISOString().split('T')[0],
     new_candidates: candidates.length,
+    deduped_by_ledger: dedupedByLedger,
     by_suggested_skill: bySkill,
     candidates,
   };
@@ -97,6 +109,7 @@ async function main() {
 
   console.log(`\n=== Discovery Report ===`);
   console.log(`New relevant URLs found: ${candidates.length}`);
+  console.log(`Excluded by decision ledger: ${dedupedByLedger}`);
   console.log('By skill:', JSON.stringify(bySkill, null, 2));
   if (candidates.length > 0) {
     console.log('\nNewest 10:');