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The Site job fails when the data file is out of date or a page asks for a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/note_editor.cpp

@@ -1,3 +1,4 @@
+#include "app_keys.h"
 #include "note_editor.h"
 
 #include <Arduino.h>
@@ -183,15 +184,8 @@ bool NoteEditor::save() {
 }
 
 void NoteEditor::help(std::vector<KeyHelp>& out) const {
-    if (dialog_) return help::dialog(out);
-    out.push_back({"Enter", "a new line"});
-    out.push_back({"Del", "delete backwards"});
-    out.push_back({"Tab", "two spaces"});
-    out.push_back({"Fn ; . , /", "move the cursor"});
-    out.push_back({"Alt Fn ; .", "a page up, down"});
-    out.push_back({"Ctrl a  e", "start, end of the line"});
-    out.push_back({"opt ' e", "an accent: \xC3\xA9"});
-    out.push_back({"`", "done: it saves by itself"});
+    if (dialog_) return keys::add(out, keys::kDialog);
+    keys::add(out, keys::kNotesEditor);
 }
 
 bool NoteEditor::onKey(const KeyEvent& e) {