refactor: restructure to clean architecture

fix: restore ScoringConfig improvements lost in refactor commit

docs: rewrite README and CLAUDE.md to reflect current architecture

code-format

code fixes

tests/EtfScorer.test.js

@@ -0,0 +1,31 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { EtfScorer } from '../src/screener/scorers/EtfScorer.js';
+
+const rules = {
+  gates: { maxExpenseRatio: 0.5 },
+  weights: { yield: 2, lowCost: 3 },
+  thresholds: { minYield: 1.5, maxExpense: 0.1, minVolume: 500000 },
+};
+
+test('rejects ETF with expense ratio above gate', () => {
+  const result = EtfScorer.score({ expenseRatio: 0.8, yield: 2.0 }, rules);
+  assert.equal(result.label, '🔴 REJECT');
+});
+
+test('efficient label for low-cost, high-yield ETF', () => {
+  const result = EtfScorer.score({ expenseRatio: 0.03, yield: 2.0, volume: 1000000 }, rules);
+  assert.equal(result.label, '🟢 Efficient');
+});
+
+test('neutral when yield is below threshold', () => {
+  const result = EtfScorer.score({ expenseRatio: 0.03, yield: 0.4, volume: 1000000 }, rules);
+  assert.equal(result.label, '🟡 Neutral');
+});
+
+test('audit breakdown includes cost, yield, vol keys', () => {
+  const result = EtfScorer.score({ expenseRatio: 0.03, yield: 2.0, volume: 1000000 }, rules);
+  assert(result.audit.breakdown.cost != null);
+  assert(result.audit.breakdown.yield != null);
+  assert(result.audit.breakdown.vol != null);
+});