fix: rebuild FTS5 index after database rebuild to prevent stale rowid refs

The FTS5 content-synced index could retain phantom rowid references from
previous rebuild cycles, causing 'missing row N from content table'
errors on MATCH queries.

- Add explicit FTS5 rebuild command in rebuild script after all nodes saved
- Add FTS5 rebuild in test beforeAll as defense-in-depth
- Rebuild nodes.db with consistent FTS5 index

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dist/scripts/rebuild.js

@@ -130,6 +130,9 @@ async function rebuild() {
         }
     }
     console.log(`💾 Save completed: ${saved} nodes saved successfully`);
+    console.log('\n🔍 Rebuilding FTS5 search index...');
+    db.prepare("INSERT INTO nodes_fts(nodes_fts) VALUES('rebuild')").run();
+    console.log('✅ FTS5 index rebuilt successfully');
     console.log('\n🔍 Running validation checks...');
     try {
         const validationResults = validateDatabase(repository);