fix(sqlite): normalize column names in ALTER TABLE ADD/DROP COLUMN

Fixes #4307

When ALTER TABLE ADD COLUMN or DROP COLUMN statements use mixed-case
column names (e.g., barBaz), the column name was stored in the catalog
with its original case. However, SELECT queries normalize all unquoted
identifiers to lowercase via the identifier() function, causing a
mismatch and 'column does not exist' errors.

This fix ensures ALTER TABLE ADD/DROP COLUMN also normalize column names
using identifier(), matching the behavior of CREATE TABLE and SELECT
queries. This aligns with SQLite's case-insensitive identifier handling.

Changes:
- internal/engine/sqlite/convert.go: Apply identifier() to column names
  in ALTER TABLE ADD COLUMN and DROP COLUMN handlers
- internal/engine/sqlite/catalog_test.go: Add regression test for
  mixed-case column names in ALTER TABLE ADD COLUMN

Author: User

internal/engine/sqlite/catalog_test.go

@@ -82,6 +82,38 @@ func TestUpdate(t *testing.T) {
 				},
 			},
 		},
+		{
+			// Regression test for #4307: mixed-case column name in ALTER TABLE ADD COLUMN
+			`
+			CREATE TABLE foo (id INTEGER NOT NULL, xYz INTEGER NOT NULL DEFAULT 0);
+			ALTER TABLE foo ADD COLUMN barBaz TEXT NOT NULL DEFAULT '';
+			`,
+			&catalog.Schema{
+				Name: "main",
+				Tables: []*catalog.Table{
+					{
+						Rel: &ast.TableName{Name: "foo"},
+						Columns: []*catalog.Column{
+							{
+								Name:      "id",
+								Type:      ast.TypeName{Name: "INTEGER"},
+								IsNotNull: true,
+							},
+							{
+								Name:      "xyz",
+								Type:      ast.TypeName{Name: "INTEGER"},
+								IsNotNull: true,
+							},
+							{
+								Name:      "barbaz",
+								Type:      ast.TypeName{Name: "TEXT"},
+								IsNotNull: true,
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			`
 			CREATE TABLE foo (bar text);

internal/engine/sqlite/convert.go

@@ -67,7 +67,7 @@ func (c *cc) convertAlter_table_stmtContext(n *parser.Alter_table_stmtContext) a
 				Table: parseTableName(n),
 				Cmds:  &ast.List{},
 			}
-			name := def.Column_name().GetText()
+			name := identifier(def.Column_name().GetText())
 			stmt.Cmds.Items = append(stmt.Cmds.Items, &ast.AlterTableCmd{
 				Name:    &name,
 				Subtype: ast.AT_AddColumn,
@@ -88,7 +88,7 @@ func (c *cc) convertAlter_table_stmtContext(n *parser.Alter_table_stmtContext) a
 			Table: parseTableName(n),
 			Cmds:  &ast.List{},
 		}
-		name := n.Column_name(0).GetText()
+		name := identifier(n.Column_name(0).GetText())
 		stmt.Cmds.Items = append(stmt.Cmds.Items, &ast.AlterTableCmd{
 			Name:    &name,
 			Subtype: ast.AT_DropColumn,