Read config.toml, keys.toml and themes, and open them with :config (stage 8b)

The config folder now sets everything: config.toml the settings (now
also `theme` and `editor`), keys.toml the keys, and themes/<name>.toml
the theme, laid over the built-in one, so a theme only needs what it
changes. Each file is applied again a second after it's saved; a
mistake only drops its own line, and the status bar says what's wrong,
naming the file.

:config lists the three files with their folder; Enter hands the
terminal to your editor (the editor setting, $VISUAL, $EDITOR, else
notepad or vi), writing the file first if it's missing, with every
option at its default behind a #, explained (keys.toml lists every
command by name). :theme switches themes until cumulus quits, like
:set.

The built-in theme gets the named styles the user picked, each also put
on by its tag: question (yellow, dashed), important (red, thick) and done
(gray, its title faded); and link styles blocks and supports, whose
label shows on a link without its own. Themes can also set [modes],
[node], [root], [branch] and [link].

Co-Authored-By: Claude Opus 5.5 <[email protected]>

examples/canvas.rs

@@ -15,9 +15,8 @@ use std::io;
 use cumulus::app::action::Message;
 use cumulus::app::startup::Opening;
 use cumulus::app::{App, load, run};
+use cumulus::config::Config;
 use cumulus::config::paths::Paths;
-use cumulus::config::settings::Settings;
-use cumulus::input::keymap::{DEFAULT_LEADER, Keymap};
 
 fn main() -> io::Result<()> {
     let folder = std::env::temp_dir().join(format!("cumulus-playground-{}", std::process::id()));
@@ -31,7 +30,8 @@ fn main() -> io::Result<()> {
         message: Some(Message::info("the playground: copies of the samples, in a temporary folder")),
     };
     let paths = Paths::inside(&folder.join("cumulus"));
-    run(App::new(paths, Settings::default(), Keymap::new(DEFAULT_LEADER), opening))?;
+    let config = Config::load(&paths);
+    run(App::new(paths, config, opening))?;
     println!("The playground's files are in {}", folder.display());
     Ok(())
 }