feat: Phase 0 workspace, spikes, and golden harness

Stand up the monorepo skeleton and land the first Phase 0 artifacts:
pairing threat model, plugin catalog, builder detect, 20-prompt golden
harness, and synthetic 2GB mirror timing.

e2e/golden/src/subset.ts

@@ -0,0 +1,16 @@
+import type { SiteExport, SubsetRequest, SubsetResult } from './types.ts';
+
+const contentTables = new Set(['wp_posts', 'wp_postmeta', 'wp_options']);
+const secret = /(_key|_secret|smtp_pass)$/;
+
+export function exportDbSubset(dump: SiteExport, request: SubsetRequest): SubsetResult {
+  const tables = Object.keys(dump.tables).filter((name) => contentTables.has(name));
+  const options = (dump.tables.wp_options ?? [])
+    .map((row) => String(row.option_name ?? ''))
+    .filter((name) => name !== '' && !secret.test(name));
+
+  if (request.playbook === 'content') {
+    return { tables, options };
+  }
+  return { tables, options };
+}