Help: consume CommandNode.help_id — REGISTRY-driven in-app help

Every CommandNode declared a help_id that nothing read; the in-app
`help` body was a single hand-kept catalog block that drifted from
the command set (handoff-12 §2.1).

note_help now iterates the command REGISTRY and translates each
CommandNode's help_id (`help.<id>`), framed by help.intro /
help.dsl_section / help.types_reference. A newly-registered command
appears in `help` automatically — no edit to note_help or a hand-kept
list. Added 20 per-command help entries plus the 3 framing entries;
removed help.in_app_body.

Per-command entries use block scalars: a libyml 0.0.5 scanner bug
panics on long internal space runs in double-quoted scalars, and the
entries are space-aligned.

src/app.rs

@@ -1595,22 +1595,46 @@ impl App {
         }
     }
 
-    /// Note a flat list of currently-supported app-level
-    /// commands to the output panel.
+    /// Note the list of currently-supported commands to the
+    /// output panel.
     ///
-    /// This is the simple Iteration-4 stand-in for a richer
-    /// help system (H3 in the requirements doc); it gives the
-    /// user a quick "what can I type?" reference that's
-    /// always accurate against the build they're running. As
-    /// new commands land, append them here.
+    /// Assembled from the command REGISTRY (ADR-0024 §help_id):
+    /// the framing (`help.intro`, `help.dsl_section`,
+    /// `help.types_reference`) comes from the catalog, and each
+    /// command's body is the catalog entry named by its
+    /// `help_id`. A newly-registered command appears here
+    /// automatically — no edit to this function or a hand-kept
+    /// list. Each catalog line becomes its own `OutputLine` so
+    /// the scroll-position math (one logical line = one display
+    /// row) stays accurate per the renderer's invariant.
     fn note_help(&mut self) {
-        // Body lives in the i18n catalog (`help.in_app_body`).
-        // Each YAML line becomes its own `OutputLine` so the
-        // scroll-position math (one logical line = one display
-        // row) stays accurate per the renderer's invariant.
-        let body = crate::t!("help.in_app_body");
-        for line in body.lines() {
-            self.note_system(line.to_string());
+        use crate::dsl::grammar::REGISTRY;
+
+        let mut lines: Vec<String> = Vec::new();
+        lines.push(crate::t!("help.intro"));
+        // REGISTRY is ordered app-commands first; emit the
+        // "DSL data commands" sub-header at the first command
+        // whose help_id leaves the `app.` namespace.
+        let mut dsl_header_done = false;
+        for command in REGISTRY {
+            let Some(help_id) = command.help_id else {
+                continue;
+            };
+            if !dsl_header_done && !help_id.starts_with("app.") {
+                lines.push(crate::t!("help.dsl_section"));
+                dsl_header_done = true;
+            }
+            let key = format!("help.{help_id}");
+            let body = crate::friendly::translate(&key, &[]);
+            lines.extend(body.lines().map(str::to_string));
+        }
+        lines.extend(
+            crate::t!("help.types_reference")
+                .lines()
+                .map(str::to_string),
+        );
+        for line in lines {
+            self.note_system(line);
         }
     }