fix: correct misleading comments and cache role UPDATE stmts (#606)

- Fix misleading "single nodeIdMap pass" comment in insertChildrenAndEdges
  (actually two passes: one before and one after batchInsertNodes)
- Cache role UPDATE prepared statements per chunk size in classifyNodeRoles,
  consistent with WeakMap-based caching pattern used in helpers.ts

Impact: 2 functions changed, 4 affected

Author: carlos-alm

src/domain/graph/builder/stages/insert-nodes.ts

@@ -86,7 +86,7 @@ function insertDefinitionsAndExports(
   }
 }
 
-// ── Phase 2+3: Insert children and containment edges (single nodeIdMap pass) ──
+// ── Phase 2+3: Insert children and containment edges (two nodeIdMap passes) ──
 
 function insertChildrenAndEdges(
   db: BetterSqlite3.Database,
@@ -96,7 +96,7 @@ function insertChildrenAndEdges(
   const edgeRows: unknown[][] = [];
 
   for (const [relPath, symbols] of allSymbols) {
-    // Single bulkNodeIdsByFile call per file, shared across children + edges
+    // First pass: collect file→def edges and child rows
     const nodeIdMap = new Map<string, number>();
     for (const row of bulkNodeIdsByFile(db, relPath)) {
       nodeIdMap.set(`${row.name}|${row.kind}|${row.line}`, row.id);

src/features/structure.ts

@@ -485,16 +485,22 @@ export function classifyNodeRoles(db: BetterSqlite3Database): RoleSummary {
 
   // Batch UPDATE: one statement per role instead of one per node
   const ROLE_CHUNK = 500;
+  const roleStmtCache = new Map<number, SqliteStatement>();
   db.transaction(() => {
     db.prepare('UPDATE nodes SET role = NULL').run();
     for (const [role, ids] of idsByRole) {
       for (let i = 0; i < ids.length; i += ROLE_CHUNK) {
         const end = Math.min(i + ROLE_CHUNK, ids.length);
         const chunkSize = end - i;
-        const placeholders = Array.from({ length: chunkSize }, () => '?').join(',');
+        let stmt = roleStmtCache.get(chunkSize);
+        if (!stmt) {
+          const placeholders = Array.from({ length: chunkSize }, () => '?').join(',');
+          stmt = db.prepare(`UPDATE nodes SET role = ? WHERE id IN (${placeholders})`);
+          roleStmtCache.set(chunkSize, stmt);
+        }
         const vals: unknown[] = [role];
         for (let j = i; j < end; j++) vals.push(ids[j]);
-        db.prepare(`UPDATE nodes SET role = ? WHERE id IN (${placeholders})`).run(...vals);
+        stmt.run(...vals);
       }
     }
   })();