Keys: one table file for the device's help panel and the website's key tables (#72)

Every screen's keys are constant tables in lib/core/src/app_keys.h (52 of
them, each under an `// id: Title` comment). An App's help() picks the table
of the state it is in. site/tools/gen_dev_docs.py reads the same file and
writes site/data/keys.toml; the `keys` shortcode shows a screen's tables on
its guide page, and /guide/keys/ shows all of them.

The Site job fails when the data file is out of date or a page asks for a
table that doesn't exist, and now also runs when app_keys.h changes. A key
added to an App shows up on the website without anyone editing a page.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/apps/notes_app.cpp

@@ -1,3 +1,4 @@
+#include "app_keys.h"
 #include "notes_app.h"
 
 #include <Arduino.h>
@@ -175,15 +176,10 @@ std::string NotesApp::titleOf(int row) {
 
 void NotesApp::help(std::vector<KeyHelp>& out) const {
     if (view_ == View::Edit) return editor_.help(out);
-    if (dialog_) return help::dialog(out);
-    if (view_ == View::Name) return help::textEntry(out, "rename the file");
+    if (dialog_) return keys::add(out, keys::kDialog);
+    if (view_ == View::Name) return keys::add(out, keys::kNotesName);
     if (view_ == View::NoMemory) return;
-    help::list(out, "open the note");
-    out.push_back({", /", "a page up, down"});
-    out.push_back({"n", "a new note"});
-    out.push_back({"r", "rename its file"});
-    out.push_back({"d  Del", "delete it"});
-    out.push_back({"s", "sort: newest, or by name"});
+    keys::add(out, keys::kNotes);
 }
 
 const char* NotesApp::helpTitle() const {