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/friendly/keys.rs

@@ -180,7 +180,8 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     // In-app `help` — framing + per-command entries keyed by
     // each CommandNode's `help_id` (ADR-0024 §help_id).
     ("help.intro", &[]),
-    ("help.dsl_section", &[]),
+    ("help.simple_section", &[]),
+    ("help.advanced_section", &[]),
     ("help.types_reference", &[]),
     ("help.detail_hint", &[]),
     ("help.unknown_topic", &["topic"]),
@@ -223,6 +224,13 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     ("help.data.delete", &[]),
     ("help.data.replay", &[]),
     ("help.data.explain", &[]),
+    // Issue #36: advanced-mode (SQL) help pages.
+    ("help.data.select", &[]),
+    ("help.data.with", &[]),
+    ("help.data.sql_insert", &[]),
+    ("help.data.sql_update", &[]),
+    ("help.data.sql_delete", &[]),
+    ("help.data.explain_sql", &[]),
     // ---- Hint panel ambient typing assistance (ADR-0022 §6) ----
     ("hint.ambient_complete", &[]),
     ("hint.ambient_error_with_usage", &["message", "usage"]),