🧹 fix: Traverse Filtered Metadata, Not Raw Metadata, In debugTraverse

`debugTraverse` computes `extracted = extractMetaObject(metadata)` to
strip reserved keys, underscore-prefixed internals, and numeric splat
artifacts — but the later \`klona(metadata)\` + \`traverse\` path still
read the raw object, putting all the filtered junk back into the
rendered multi-line output.

Clone and traverse \`debugValue\` (the already-filtered object) instead.
Regression test exercises the case where numeric splat artifacts sit
alongside a real metadata field.

Reviewed-by: Codex (P2 finding on PR #12737, commit c29c18e8).

api/config/__tests__/parsers.spec.js

@@ -256,6 +256,23 @@ describe('debugTraverse', () => {
     expect(tenantMatches.length).toBe(1);
   });
 
+  it('omits numeric splat-artifact keys from the traversed output', () => {
+    const info = {
+      level: 'error',
+      message: 'boom',
+      timestamp: 'ts',
+      0: 'x',
+      1: 'y',
+      realField: 'keep',
+      [SPLAT_SYMBOL]: [{ realField: 'keep' }],
+    };
+    const out = runFormatter(info);
+    expect(out).toContain('realField');
+    expect(out).toContain('keep');
+    expect(out).not.toMatch(/^\s*0:/m);
+    expect(out).not.toMatch(/^\s*1:/m);
+  });
+
   it('surfaces unconsumed primitive SPLAT[0] (no %s in message) for debug level', () => {
     const info = {
       level: 'debug',

api/config/parsers.js

@@ -241,7 +241,13 @@ const debugTraverse = winston.format.printf(({ level, message, timestamp, ...met
 
     msg += '\n{';
 
-    const copy = klona(metadata);
+    /*
+     * Traverse the filtered metadata (`debugValue`), not the raw `metadata`
+     * object. `extractMetaObject` strips reserved keys, underscore-prefixed
+     * internals, and numeric-string splat artifacts — re-reading from raw
+     * `metadata` here would put those artifacts back into the output.
+     */
+    const copy = klona(debugValue);
     traverse(copy).forEach(function (value) {
       if (typeof this?.key === 'symbol') {
         return;