Fix EPHEMERAL column parsing to not consume COMMENT keyword

When parsing EPHEMERAL columns, don't treat COMMENT, TTL, PRIMARY,
or SETTINGS as part of the default expression. These are column
modifiers that should be parsed separately.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

parser/parser.go

@@ -4340,8 +4340,10 @@ func (p *Parser) parseColumnDeclaration() *ast.ColumnDeclaration {
 	if p.currentIs(token.IDENT) && strings.ToUpper(p.current.Value) == "EPHEMERAL" {
 		col.DefaultKind = "EPHEMERAL"
 		p.nextToken()
-		// Optional default value
-		if !p.currentIs(token.COMMA) && !p.currentIs(token.RPAREN) && !p.currentIs(token.IDENT) {
+		// Optional default value - but don't parse column keywords (CODEC, COMMENT, TTL, etc.) as expressions
+		if !p.currentIs(token.COMMA) && !p.currentIs(token.RPAREN) && !p.currentIs(token.IDENT) &&
+			!p.currentIs(token.COMMENT) && !p.currentIs(token.TTL) && !p.currentIs(token.PRIMARY) &&
+			!p.currentIs(token.SETTINGS) {
 			col.Default = p.parseExpression(LOWEST)
 		}
 	}

parser/testdata/03250_ephemeral_comment/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true
-  }
-}
+{}