Add support for SHOW SETTING (singular) query

Add ShowSetting as a separate ShowType from ShowSettings (plural).
When parsing SHOW queries, detect "SETTING" as an IDENT and set the
appropriate type. This fixes 3 statements in 02905_show_setting_query
and 3 statements in 00405_output_format_pretty_color.

Author: claude

ast/ast.go

@@ -810,6 +810,7 @@ const (
 	ShowDictionaries            ShowType = "DICTIONARIES"
 	ShowFunctions               ShowType = "FUNCTIONS"
 	ShowSettings                ShowType = "SETTINGS"
+	ShowSetting                 ShowType = "SETTING"
 	ShowGrants                  ShowType = "GRANTS"
 )
 

parser/parser.go

@@ -5838,6 +5838,8 @@ func (p *Parser) parseShow() ast.Statement {
 				show.ShowType = ast.ShowDictionaries
 			case "FUNCTIONS":
 				show.ShowType = ast.ShowFunctions
+			case "SETTING":
+				show.ShowType = ast.ShowSetting
 			case "INDEXES", "INDICES", "KEYS":
 				// SHOW INDEXES/INDICES/KEYS FROM table - treat as ShowColumns
 				show.ShowType = ast.ShowColumns

parser/testdata/00405_output_format_pretty_color/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt13": true,
-    "stmt22": true,
-    "stmt4": true
-  }
-}
+{}

parser/testdata/02905_show_setting_query/metadata.json

@@ -1,7 +1,2 @@
 {
-  "explain_todo": {
-    "stmt2": true,
-    "stmt4": true,
-    "stmt5": true
-  }
 }