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/files.rs

@@ -315,9 +315,10 @@ impl App {
     }
 
     /// Looks at every file for changes made outside cumulus, and lets
-    /// read-only documents be edited once the other cumulus lets go.
+    /// read-only documents be edited once the other cumulus lets go. The
+    /// config files saved since they were read apply again.
     fn watch(&mut self) -> bool {
-        let mut said = Vec::new();
+        let mut said = self.reread_config();
         for id in self.shared.docs.ids() {
             said.extend(self.look_at(id));
             let open = self.shared.docs.get_mut(id);