Fix CSV loader to handle out-of-order and subset columns

- Parse CSV header to extract column names and order
- Use COPY table (col1, col2, ...) FROM STDIN WITH CSV HEADER to specify column order
- Handle BOM, whitespace, and quoted column names
- Validate column names against SQL identifier rules
- Fix posts-subset-header.csv to have correct test data values

This allows CSV files to have columns in any order and only include a subset of table columns, as long as omitted columns are nullable or have defaults.

Co-Authored-By: Dan Lynch <pyramation@gmail.com>

Author: pyramation

packages/pgsql-test/csv/posts-subset-header.csv

@@ -1,3 +1,3 @@
 id,content,user_id
-1,'sdf',1
-2,'sdf',2
+1,Hello world!,1
+2,Graphile is cool!,2

packages/pgsql-test/src/seed/csv.ts

@@ -1,4 +1,5 @@
 import { pipeline } from 'node:stream/promises';
+import { createInterface } from 'node:readline';
 
 import { Logger } from '@launchql/logger';
 import { createReadStream, createWriteStream,existsSync } from 'fs';
@@ -28,9 +29,68 @@ export function csv(tables: CsvSeedMap): SeedAdapter {
   };
 }
 
+/**
+ * Parse and validate CSV header columns
+ */
+async function parseCsvHeader(filePath: string): Promise<string[]> {
+  const fileStream = createReadStream(filePath);
+  const rl = createInterface({
+    input: fileStream,
+    crlfDelay: Infinity
+  });
+
+  let headerLine: string | null = null;
+  
+  for await (const line of rl) {
+    headerLine = line;
+    break; // Only read the first line
+  }
+
+  rl.close();
+  fileStream.destroy();
+
+  if (!headerLine) {
+    throw new Error('CSV file is empty or has no header');
+  }
+
+  if (headerLine.charCodeAt(0) === 0xFEFF) {
+    headerLine = headerLine.slice(1);
+  }
+
+  const columns = headerLine.split(',').map(col => {
+    let cleaned = col.trim();
+    if ((cleaned.startsWith('"') && cleaned.endsWith('"')) ||
+        (cleaned.startsWith("'") && cleaned.endsWith("'"))) {
+      cleaned = cleaned.slice(1, -1);
+    }
+    return cleaned.toLowerCase();
+  });
+
+  const validIdentifier = /^[a-z_][a-z0-9_]*$/;
+  for (const col of columns) {
+    if (!validIdentifier.test(col)) {
+      throw new Error(`Invalid column name in CSV header: "${col}". Column names must be valid SQL identifiers.`);
+    }
+  }
+
+  if (columns.length === 0) {
+    throw new Error('CSV header has no columns');
+  }
+
+  return columns;
+}
+
 export async function copyCsvIntoTable(pg: PgTestClient, table: string, filePath: string): Promise<void> {
   const client: Client = pg.client;
-  const stream = client.query(copyFrom(`COPY ${table} FROM STDIN WITH CSV HEADER`));
+  
+  const columns = await parseCsvHeader(filePath);
+  
+  const columnList = columns.join(', ');
+  const copyCommand = `COPY ${table} (${columnList}) FROM STDIN WITH CSV HEADER`;
+  
+  log.info(`Using columns: ${columnList}`);
+  
+  const stream = client.query(copyFrom(copyCommand));
   const source = createReadStream(filePath);
 
   try {