feat(help): distinct help for advanced-mode SQL forms; split list by mode (#36)

The six advanced SQL DML/query forms (SELECT, WITH, SQL_INSERT, SQL_UPDATE,
SQL_DELETE, EXPLAIN_SQL) carried help_id: None, so `help select`/`help with`
resolved to nothing and `help insert` showed only the simple form. Give each
its own distinct help_id (data.select, data.sql_insert, …) with a hand-curated
help.data.* page. Distinct strings keep the dedup invariant intact, and
note_help_topic needs no change — `help insert` now shows the simple block and
the sql_insert block (like `help create` already did), and the advanced-only
forms resolve.

note_help now groups the list by CommandCategory: app-lifecycle commands first
(unlabelled), then "Simple-mode commands:" and "Advanced-mode (SQL) commands:"
sections — replacing the old single "DSL data commands (in simple mode):"
header, which used the banned "DSL" term and mis-labelled the advanced SQL
forms it already contained.

Four new help_command tests (red→green). Recorded as ADR-0024 Amendment 1;
CHANGELOG updated.

src/dsl/grammar/mod.rs

@@ -537,8 +537,11 @@ pub struct CommandNode {
     /// block). `hint_key_for_input_in_mode` disambiguates by the form
     /// word, reusing `usage_key_for_input_in_mode`'s logic. Empty
     /// until a form's tier-3 block is authored (the surface falls back
-    /// to tier-2 ambient/error text). Distinct from `help_id` (which is
-    /// `None` on advanced-SQL forms purely to dedup the `help` list).
+    /// to tier-2 ambient/error text). Parallel to `help_id` but
+    /// finer-grained: every form (simple and advanced) carries a
+    /// `hint_id`, whereas the `help <topic>` view groups forms by entry
+    /// word (so a shared-entry simple + SQL pair both surface under e.g.
+    /// `help insert`).
     pub hint_ids: &'static [&'static str],
     /// Catalog keys under `parse.usage.*` to render in the
     /// "usage:" block when a parse error fires for this command
@@ -1156,10 +1159,12 @@ mod usage_key_tests {
     #[test]
     fn no_two_registered_commands_share_a_help_id() {
         // `note_help` emits one help block per `help_id: Some(_)`
-        // with no dedup, so a duplicate help_id prints the same
-        // command twice in `help`. Shared-entry-word `Advanced`
-        // nodes (SQL_INSERT, …, EXPLAIN_SQL) therefore carry
-        // `help_id: None` and defer to their `Simple` sibling.
+        // with no dedup, so a duplicate help_id string prints the same
+        // block twice. Distinct help_ids are fine — a shared-entry-word
+        // simple + SQL pair (e.g. `data.insert` + `data.sql_insert`,
+        // issue #36) each get their own block, grouped under one topic
+        // by `help <topic>` and split across the simple/advanced
+        // sections of the full list.
         let mut seen = std::collections::HashSet::new();
         for (command, _category) in super::REGISTRY {
             if let Some(id) = command.help_id {