fix(plpgsql-deparser): filter out implicit sqlstate/sqlerrm variables

PostgreSQL automatically adds sqlstate and sqlerrm variables for exception
handling. These should not be explicitly declared in the output DECLARE section.

Updated snapshots to reflect the fix.

Author: pyramation

packages/plpgsql-deparser/__tests__/__snapshots__/hydrate-demo.test.ts.snap

@@ -49,8 +49,6 @@ exports[`hydrate demonstration with big-function.sql should parse, hydrate, modi
   v_sql text;
   v_rowcount int := 0;
   v_lock_key bigint := CAST(CAST('x' || substr(md5(p_org_id::text), 1, 16) AS pg_catalog.bit(64)) AS bigint);
-  sqlstate CONSTANT text;
-  sqlerrm CONSTANT text;
 BEGIN
   BEGIN
       IF p_org_id IS NULL

packages/plpgsql-deparser/src/plpgsql-deparser.ts

@@ -342,8 +342,11 @@ export class PLpgSQLDeparser {
     const localVars = datums.filter(datum => {
       if ('PLpgSQL_var' in datum) {
         const v = datum.PLpgSQL_var;
-        // Skip internal variables
-        if (v.refname === 'found' || v.refname.startsWith('__')) {
+        // Skip internal variables:
+        // - 'found' is the implicit FOUND variable
+        // - 'sqlstate' and 'sqlerrm' are implicit exception handling variables
+        // - variables starting with '__' are internal
+        if (v.refname === 'found' || v.refname === 'sqlstate' || v.refname === 'sqlerrm' || v.refname.startsWith('__')) {
           return false;
         }
         // Skip variables without lineno (usually parameters or internal)