Rewrite version() to return PostgreSQL-compatible string

PostgreSQL clients call SELECT version() to check database compatibility.
DuckDB's native version() returns "v1.1.0 ..." which doesn't match
PostgreSQL format and can't be overridden by macros.

This rewrites version() calls to return a PostgreSQL-compatible string:
"PostgreSQL 15.0 on x86_64-pc-linux-gnu, compiled by gcc, 64-bit (Duckgres/DuckDB)"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: EDsCODE

server/catalog.go

@@ -364,6 +364,8 @@ var (
 	showApplicationNameRegex = regexp.MustCompile(`(?i)^SHOW\s+application_name\s*;?\s*$`)
 	// Regex to extract SET parameter name
 	setParameterRegex = regexp.MustCompile(`(?i)^SET\s+(?:SESSION\s+|LOCAL\s+)?(\w+)`)
+	// version() -> PostgreSQL-compatible version string (DuckDB's built-in can't be overridden by macro)
+	versionFuncRegex = regexp.MustCompile(`(?i)\bversion\s*\(\s*\)`)
 )
 
 // PostgreSQL-specific SET parameters that DuckDB doesn't support.
@@ -554,6 +556,10 @@ func rewritePgCatalogQuery(query string) string {
 	query = setApplicationNameToRegex.ReplaceAllString(query, "SET VARIABLE application_name =")
 	query = showApplicationNameRegex.ReplaceAllString(query, "SELECT getvariable('application_name') AS application_name")
 
+	// Replace version() with PostgreSQL-compatible version string
+	// DuckDB's built-in version() can't be overridden by macros
+	query = versionFuncRegex.ReplaceAllString(query, "'PostgreSQL 15.0 on x86_64-pc-linux-gnu, compiled by gcc, 64-bit (Duckgres/DuckDB)'")
+
 	return query
 }