feat: V5 show tables / relationships / indexes list commands

Add the list-all show family as one Command::ShowList { kind }
variant. A read-only worker show_list formats count-headed lists
(reusing do_list_tables / read_all_relationships /
read_table_indexes, so it never drifts from the items panel);
internal __rdbms_* tables excluded. Help + parse-usage entries
added; 10 integration tests in tests/it/show_list.rs.

Mark V5 [x]. Split the singular show relationship/index <name>
detail forms (the [<name>] half) into a new tracked V5a [ ] item
rather than leaving them as an untracked footnote.

src/runtime.rs

@@ -1403,6 +1403,10 @@ fn spawn_dsl_dispatch(
                     echo,
                 }
             }
+            Ok(CommandOutcome::ShowList(lines)) => AppEvent::DslShowListSucceeded {
+                command: command.clone(),
+                lines,
+            },
             Ok(CommandOutcome::QueryPlan(plan)) => AppEvent::DslExplainSucceeded {
                 command: command.clone(),
                 plan,
@@ -2244,6 +2248,10 @@ enum CommandOutcome {
     /// — skipped" note.
     SchemaCreateIndexSkipped(String),
     Query(DataResult),
+    /// A `show <kind>` list (V5) — pre-formatted display lines from
+    /// the worker (table / relationship / index names). Pure
+    /// display, no schema change.
+    ShowList(Vec<String>),
     QueryPlan(QueryPlan),
     Insert(InsertResult),
     Update(UpdateResult),
@@ -2766,6 +2774,9 @@ async fn execute_command_typed(
             .describe_table(name, src)
             .await
             .map(|d| CommandOutcome::Schema(Some(d))),
+        Command::ShowList { kind } => {
+            database.show_list(kind).await.map(CommandOutcome::ShowList)
+        }
         Command::Insert {
             table,
             columns,