Fix unclosed bracket doubling last char and set operation SQL generation

- raHighlight.ts: Check that code[newI-1] is actually a bracket char
  before rendering it as a closing bracket. Previously, unclosed brackets
  like PI[name, city would render the last content char twice (cityy).
- relationalAlgebra.ts: Add asSelect() helper to wrap bare table names
  in SELECT * FROM for UNION/INTERSECT/EXCEPT operations. Previously
  Person-Teacher generated "Person EXCEPT Teacher" which SQLite rejected.

https://claude.ai/code/session_01TJyw8nESra9cc5RpVUpmt6

Author: claude

src/raHighlight.ts

@@ -217,10 +217,12 @@ function renderSubscript(code: string, i: number, result: string[]): number {
     const [newI, content] = extractBracketContent(code, i);
     if (content !== null) {
       result.push(`<span style="${S.sub}">${highlightSubContent(content, subWrap)}</span>`);
-      // Render closing bracket
-      if (newI > i + 1) {
+      // Render closing bracket (only if bracket was actually closed)
+      if (newI > i + 1 && newI <= code.length) {
         const closeBracket = code[newI - 1];
-        result.push(`<span style="${S.bracket}">${esc(closeBracket)}</span>`);
+        if (closeBracket === "]" || closeBracket === "}") {
+          result.push(`<span style="${S.bracket}">${esc(closeBracket)}</span>`);
+        }
       }
       return newI;
     }

src/relationalAlgebra.ts

@@ -1057,6 +1057,13 @@ function resolveColumns(sql: string, db: DatabaseHandle): string[] {
     throw new RAError(msg);
   }
 }
+/** Ensure a node produces a full SELECT statement (needed for UNION/INTERSECT/EXCEPT) */
+function asSelect(node: RANode, db?: DatabaseHandle): string {
+  const sql = nodeToSQL(node, db);
+  // Bare table names need wrapping; anything starting with SELECT is already a query
+  return sql.trimStart().toUpperCase().startsWith("SELECT") ? sql : `SELECT * FROM ${sql}`;
+}
+
 function nodeToSQL(node: RANode, db?: DatabaseHandle): string {
   switch (node.type) {
     case "table":
@@ -1152,13 +1159,13 @@ function nodeToSQL(node: RANode, db?: DatabaseHandle): string {
     }
 
     case "union":
-      return `${nodeToSQL(node.left, db)} UNION ${nodeToSQL(node.right, db)}`;
+      return `${asSelect(node.left, db)} UNION ${asSelect(node.right, db)}`;
 
     case "intersect":
-      return `${nodeToSQL(node.left, db)} INTERSECT ${nodeToSQL(node.right, db)}`;
+      return `${asSelect(node.left, db)} INTERSECT ${asSelect(node.right, db)}`;
 
     case "difference":
-      return `${nodeToSQL(node.left, db)} EXCEPT ${nodeToSQL(node.right, db)}`;
+      return `${asSelect(node.left, db)} EXCEPT ${asSelect(node.right, db)}`;
 
     case "division": {
       const lAlias = `_ra${subqueryCounter++}`;