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]>

src/app/input.rs

@@ -9,6 +9,7 @@ use super::mode::Mode;
 use super::{App, calls, commands};
 use crate::command::parse::{Sources, parse};
 use crate::config::settings::Setting;
+use crate::config::theme_file;
 use crate::input::command::{Bound, Command, help_for};
 use crate::input::engine::{Outcome, Typed};
 use crate::input::key::Key;
@@ -143,7 +144,7 @@ impl App {
             nodes: nodes.collect(),
             colors: theme.palette.keys().map(ToString::to_string).collect(),
             styles: theme.node_styles.keys().map(ToString::to_string).collect(),
-            themes: vec!["default".into()],
+            themes: theme_file::names(&self.paths),
             settings: Setting::ALL.iter().map(|setting| setting.name().to_string()).collect(),
             tags,
             folder: self.folder(),